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<!-- Reviewed: no -->
<sect1 id="zend.db.adapter">
    <title>Zend_Db_Adapter</title>

    <para>
        <classname>Zend_Db</classname> and its related classes provide a simple
        <acronym>SQL</acronym> database interface for Zend Framework. The
        <classname>Zend_Db_Adapter</classname> is the basic class you use to connect your
        <acronym>PHP</acronym> application to an <acronym>RDBMS</acronym>. There is a different
        Adapter class for each brand of <acronym>RDBMS</acronym>.
    </para>

    <para>
        The <classname>Zend_Db</classname> adapters create a bridge from the vendor-specific
        <acronym>PHP</acronym> extensions to a common interface to help you write
        <acronym>PHP</acronym> applications once and deploy with multiple brands of
        <acronym>RDBMS</acronym> with very little effort.
    </para>

    <para>
        The interface of the adapter class is similar to the interface of the
        <ulink url="http://www.php.net/pdo">PHP Data Objects</ulink> extension.
        <classname>Zend_Db</classname> provides Adapter classes to <acronym>PDO</acronym> drivers
        for the following <acronym>RDBMS</acronym> brands:
    </para>

    <itemizedlist>
        <listitem>
            <para>
                <acronym>IBM</acronym> <acronym>DB2</acronym> and Informix Dynamic Server
                (<acronym>IDS</acronym>), using the <ulink
                    url="http://www.php.net/pdo-ibm">pdo_ibm</ulink> <acronym>PHP</acronym>
                extension
            </para>
        </listitem>

        <listitem>
            <para>
                MariaDB, using the <ulink url="http://www.php.net/pdo-mysql">pdo_mysql</ulink>
                <acronym>PHP</acronym> extension
            </para>
        </listitem>

        <listitem>
            <para>
                MySQL, using the <ulink url="http://www.php.net/pdo-mysql">pdo_mysql</ulink>
                <acronym>PHP</acronym> extension
            </para>
        </listitem>

        <listitem>
            <para>
                Microsoft <acronym>SQL</acronym> Server, using the <ulink
                    url="http://www.php.net/pdo-dblib">pdo_dblib</ulink> <acronym>PHP</acronym>
                extension
            </para>
        </listitem>

        <listitem>
            <para>
                Oracle, using the <ulink url="http://www.php.net/pdo-oci">pdo_oci</ulink>
                <acronym>PHP</acronym> extension
            </para>
        </listitem>

        <listitem>
            <para>
                PostgreSQL, using the <ulink url="http://www.php.net/pdo-pgsql">pdo_pgsql</ulink>
                <acronym>PHP</acronym> extension
            </para>
        </listitem>

        <listitem>
            <para>
                SQLite, using the <ulink url="http://www.php.net/pdo-sqlite">pdo_sqlite</ulink>
                <acronym>PHP</acronym> extension
            </para>
        </listitem>
    </itemizedlist>

    <para>
        In addition, <classname>Zend_Db</classname> provides Adapter classes that utilize
        <acronym>PHP</acronym> database extensions for the following <acronym>RDBMS</acronym>
        brands:
    </para>

    <itemizedlist>
        <listitem>
            <para>
                MariaDB, using the <ulink url="http://www.php.net/mysqli">mysqli</ulink>
                <acronym>PHP</acronym> extension
            </para>
        </listitem>

        <listitem>
            <para>
                MySQL, using the <ulink url="http://www.php.net/mysqli">mysqli</ulink>
                <acronym>PHP</acronym> extension
            </para>
        </listitem>

        <listitem>
            <para>
                Oracle, using the <ulink url="http://www.php.net/oci8">oci8</ulink>
                <acronym>PHP</acronym> extension
            </para>
        </listitem>

        <listitem>
            <para>
                <acronym>IBM</acronym> <acronym>DB2</acronym> and <acronym>DB2</acronym> I5, using
                the <ulink url="http://www.php.net/ibm_db2">ibm_db2</ulink> <acronym>PHP</acronym>
                extension
            </para>
        </listitem>

        <listitem>
            <para>
                Firebird (Interbase), using the <ulink
                    url="http://www.php.net/ibase">php_interbase</ulink> <acronym>PHP</acronym>
                extension
            </para>
        </listitem>
    </itemizedlist>

    <note>
        <para>
            Each <classname>Zend_Db</classname> Adapter uses a <acronym>PHP</acronym> extension. You
            must have the respective <acronym>PHP</acronym> extension enabled in your
            <acronym>PHP</acronym> environment to use a <classname>Zend_Db</classname> Adapter. For
            example, if you use any of the <acronym>PDO</acronym> <classname>Zend_Db</classname>
            Adapters, you need to enable both the <acronym>PDO</acronym> extension and the
            <acronym>PDO</acronym> driver for the brand of <acronym>RDBMS</acronym> you use.
        </para>
    </note>

    <sect2 id="zend.db.adapter.connecting">
        <title>Connecting to a Database Using an Adapter</title>

        <para>
            This section describes how to create an instance of a database Adapter.
            This corresponds to making a connection to your <acronym>RDBMS</acronym> server from
            your <acronym>PHP</acronym> application.
        </para>

        <sect3 id="zend.db.adapter.connecting.constructor">
            <title>Using a Zend_Db Adapter Constructor</title>

            <para>
                You can create an instance of an adapter using its constructor.
                An adapter constructor takes one argument, which is an array
                of parameters used to declare the connection.
            </para>

            <example id="zend.db.adapter.connecting.constructor.example">
                <title>Using an Adapter Constructor</title>

                <programlisting language="php"><![CDATA[
$db = new Zend_Db_Adapter_Pdo_Mysql(array(
    'host'     => '127.0.0.1',
    'username' => 'webuser',
    'password' => 'xxxxxxxx',
    'dbname'   => 'test'
));
]]></programlisting>
            </example>
        </sect3>

        <sect3 id="zend.db.adapter.connecting.factory">
            <title>Using the Zend_Db Factory</title>

            <para>
                As an alternative to using an adapter constructor directly, you
                can create an instance of an adapter using the static method
                <methodname>Zend_Db::factory()</methodname>. This method dynamically loads
                the adapter class file on demand using
                <link linkend="zend.loader.load.class">Zend_Loader::loadClass()</link>.
            </para>

            <para>
                The first argument is a string that names the base name of the
                adapter class. For example the string '<classname>Pdo_Mysql</classname>' corresponds
                to the class <classname>Zend_Db_Adapter_Pdo_Mysql</classname>. The second argument
                is the same array of parameters you would have given to the
                adapter constructor.
            </para>

            <example id="zend.db.adapter.connecting.factory.example">
                <title>Using the Adapter Factory Method</title>

                <programlisting language="php"><![CDATA[
// We don't need the following statement because the
// Zend_Db_Adapter_Pdo_Mysql file will be loaded for us by the Zend_Db
// factory method.

// require_once 'Zend/Db/Adapter/Pdo/Mysql.php';

// Automatically load class Zend_Db_Adapter_Pdo_Mysql
// and create an instance of it.
$db = Zend_Db::factory('Pdo_Mysql', array(
    'host'     => '127.0.0.1',
    'username' => 'webuser',
    'password' => 'xxxxxxxx',
    'dbname'   => 'test'
));
]]></programlisting>
            </example>

            <para>
                If you create your own class that extends
                <classname>Zend_Db_Adapter_Abstract</classname>, but you do not name your
                class with the "<classname>Zend_Db_Adapter</classname>" package prefix, you can use
                the <methodname>factory()</methodname> method to load your adapter if you
                specify the leading portion of the adapter class with the
                'adapterNamespace' key in the parameters array.
            </para>

            <example id="zend.db.adapter.connecting.factory.example2">
                <title>Using the Adapter Factory Method for a Custom Adapter Class</title>

                <programlisting language="php"><![CDATA[
// We don't need to load the adapter class file
// because it will be loaded for us by the Zend_Db factory method.

// Automatically load class MyProject_Db_Adapter_Pdo_Mysql and create
// an instance of it.
$db = Zend_Db::factory('Pdo_Mysql', array(
    'host'             => '127.0.0.1',
    'username'         => 'webuser',
    'password'         => 'xxxxxxxx',
    'dbname'           => 'test',
    'adapterNamespace' => 'MyProject_Db_Adapter'
));
]]></programlisting>
            </example>
        </sect3>

        <sect3 id="zend.db.adapter.connecting.factory-config">
            <title>Using Zend_Config with the Zend_Db Factory</title>

            <para>
                Optionally, you may specify either argument of the
                <methodname>factory()</methodname> method as an object of type
                <link linkend="zend.config">Zend_Config</link>.
            </para>

            <para>
                If the first argument is a config object, it is expected to
                contain a property named <property>adapter</property>, containing the
                string naming the adapter class name base. Optionally, the object
                may contain a property named <property>params</property>, with
                subproperties corresponding to adapter parameter names.
                This is used only if the second argument of the
                <methodname>factory()</methodname> method is absent.
            </para>

            <example id="zend.db.adapter.connecting.factory.example1">
                <title>Using the Adapter Factory Method with a Zend_Config Object</title>

                <para>
                    In the example below, a <classname>Zend_Config</classname> object is created
                    from an array. You can also load data from an external file using classes such
                    as <link linkend="zend.config.adapters.ini">Zend_Config_Ini</link>
                    and <link linkend="zend.config.adapters.xml">Zend_Config_Xml</link>.
                </para>

                <programlisting language="php"><![CDATA[
$config = new Zend_Config(
    array(
        'database' => array(
            'adapter' => 'Mysqli',
            'params'  => array(
                'host'     => '127.0.0.1',
                'dbname'   => 'test',
                'username' => 'webuser',
                'password' => 'secret',
            )
        )
    )
);

$db = Zend_Db::factory($config->database);
]]></programlisting>
            </example>

            <para>
                The second argument of the <methodname>factory()</methodname> method may be
                an associative array containing entries corresponding to
                adapter parameters. This argument is optional. If the first
                argument is of type <classname>Zend_Config</classname>, it is assumed to contain all
                parameters, and the second argument is ignored.
            </para>
        </sect3>

        <sect3 id="zend.db.adapter.connecting.parameters">
            <title>Adapter Parameters</title>

            <para>
                The following list explains common parameters recognized by
                <classname>Zend_Db</classname> Adapter classes.
            </para>

            <itemizedlist>
                <listitem>
                    <para>
                        <emphasis>host</emphasis>:
                        a string containing a hostname or IP address of the
                        database server. If the database is running on the
                        same host as the <acronym>PHP</acronym> application, you may use
                        'localhost' or '127.0.0.1'.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <emphasis>username</emphasis>:
                        account identifier for authenticating a connection to the
                        <acronym>RDBMS</acronym> server.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <emphasis>password</emphasis>:
                        account password credential for authenticating a
                        connection to the <acronym>RDBMS</acronym> server.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <emphasis>dbname</emphasis>:
                        database instance name on the <acronym>RDBMS</acronym> server.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <emphasis>port</emphasis>:
                        some <acronym>RDBMS</acronym> servers can accept network connections on a
                        administrator-specified port number. The port
                        parameter allow you to specify the port to which your
                        <acronym>PHP</acronym> application connects, to match the port configured
                        on the <acronym>RDBMS</acronym> server.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <emphasis>charset</emphasis>:
                        specify the charset used for the connection.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <emphasis>options</emphasis>:
                        this parameter is an associative array of options
                        that are generic to all <classname>Zend_Db_Adapter</classname> classes.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <emphasis>driver_options</emphasis>:
                        this parameter is an associative array of additional
                        options that are specific to a given database
                        extension. One typical use of this parameter is to
                        set attributes of a <acronym>PDO</acronym> driver.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <emphasis>adapterNamespace</emphasis>:
                        names the initial part of the class name for the
                        adapter, instead of '<classname>Zend_Db_Adapter</classname>'. Use this if
                        you need to use the <methodname>factory()</methodname> method to
                        load a non-Zend database adapter class.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <emphasis>socket</emphasis>:
                        allows you to specify the socket or named pipe to use.
                        Currently supported only by mysqli adapter.
                    </para>
                </listitem>
            </itemizedlist>

            <example id="zend.db.adapter.connecting.parameters.example1">
                <title>Passing the Case-Folding Option to the Factory</title>

                <para>
                    You can specify this option by the constant
                    <constant>Zend_Db::CASE_FOLDING</constant>.
                    This corresponds to the <constant>ATTR_CASE</constant> attribute in
                    <acronym>PDO</acronym> and <acronym>IBM</acronym> <acronym>DB2</acronym>
                    database drivers, adjusting the case of string keys in query result sets. The
                    option takes values <constant>Zend_Db::CASE_NATURAL</constant> (the default),
                    <constant>Zend_Db::CASE_UPPER</constant>, and
                    <constant>Zend_Db::CASE_LOWER</constant>.
                </para>

                <programlisting language="php"><![CDATA[
$options = array(
    Zend_Db::CASE_FOLDING => Zend_Db::CASE_UPPER
);

$params = array(
    'host'           => '127.0.0.1',
    'username'       => 'webuser',
    'password'       => 'xxxxxxxx',
    'dbname'         => 'test',
    'options'        => $options
);

$db = Zend_Db::factory('Db2', $params);
]]></programlisting>
            </example>

            <example id="zend.db.adapter.connecting.parameters.example2">
                <title>Passing the Auto-Quoting Option to the Factory</title>

                <para>
                    You can specify this option by the constant
                    <constant>Zend_Db::AUTO_QUOTE_IDENTIFIERS</constant>. If the value
                    is <constant>TRUE</constant> (the default), identifiers like table
                    names, column names, and even aliases are delimited in all
                    <acronym>SQL</acronym> syntax generated by the Adapter object. This makes it
                    simple to use identifiers that contain <acronym>SQL</acronym> keywords, or
                    special characters. If the value is <constant>FALSE</constant>,
                    identifiers are not delimited automatically. If you need
                    to delimit identifiers, you must do so yourself using the
                    <methodname>quoteIdentifier()</methodname> method.
                </para>

                <programlisting language="php"><![CDATA[
$options = array(
    Zend_Db::AUTO_QUOTE_IDENTIFIERS => false
);

$params = array(
    'host'           => '127.0.0.1',
    'username'       => 'webuser',
    'password'       => 'xxxxxxxx',
    'dbname'         => 'test',
    'options'        => $options
);

$db = Zend_Db::factory('Pdo_Mysql', $params);
]]></programlisting>
            </example>

            <example id="zend.db.adapter.connecting.parameters.example3">
                <title>Passing PDO Driver Options to the Factory</title>

                <programlisting language="php"><![CDATA[
$pdoParams = array(
    PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => true
);

$params = array(
    'host'           => '127.0.0.1',
    'username'       => 'webuser',
    'password'       => 'xxxxxxxx',
    'dbname'         => 'test',
    'driver_options' => $pdoParams
);

$db = Zend_Db::factory('Pdo_Mysql', $params);

echo $db->getConnection()
        ->getAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY);
]]></programlisting>
            </example>

            <example id="zend.db.adapter.connecting.parameters.example4">
                <title>Passing Serialization Options to the Factory</title>

                <programlisting language="php"><![CDATA[
$options = array(
    Zend_Db::ALLOW_SERIALIZATION => false
);

$params = array(
    'host'           => '127.0.0.1',
    'username'       => 'webuser',
    'password'       => 'xxxxxxxx',
    'dbname'         => 'test',
    'options'        => $options
);

$db = Zend_Db::factory('Pdo_Mysql', $params);
]]></programlisting>
            </example>
        </sect3>

        <sect3 id="zend.db.adapter.connecting.getconnection">
            <title>Managing Lazy Connections</title>

            <para>
                Creating an instance of an Adapter class does not immediately
                connect to the <acronym>RDBMS</acronym> server. The Adapter saves the connection
                parameters, and makes the actual connection on demand, the
                first time you need to execute a query. This ensures that
                creating an Adapter object is quick and inexpensive. You can
                create an instance of an Adapter even if you are not certain
                that you need to run any database queries during the current
                request your application is serving.
            </para>

            <para>
                If you need to force the Adapter to connect to the <acronym>RDBMS</acronym>, use
                the <methodname>getConnection()</methodname> method. This method returns
                an object for the connection as represented by the respective
                <acronym>PHP</acronym> database extension. For example, if you use any of the
                Adapter classes for <acronym>PDO</acronym> drivers, then
                <methodname>getConnection()</methodname> returns the <acronym>PDO</acronym> object,
                after initiating it as a live connection to the specific database.
            </para>

            <para>
                It can be useful to force the connection if you want to catch
                any exceptions it throws as a result of invalid account
                credentials, or other failure to connect to the <acronym>RDBMS</acronym> server.
                These exceptions are not thrown until the connection is made,
                so it can help simplify your application code if you handle the
                exceptions in one place, instead of at the time of
                the first query against the database.
            </para>

            <para>
                Additionally, an adapter can get serialized to store it, for example,
                in a session variable. This can be very useful not only for the
                adapter itself, but for other objects that aggregate it, like a
                <classname>Zend_Db_Select</classname> object. By default, adapters are allowed
                to be serialized, if you don't want it, you should consider passing the
                <constant>Zend_Db::ALLOW_SERIALIZATION</constant> option with
                <constant>FALSE</constant>, see the example above. To respect lazy connections
                principle, the adapter won't reconnect itself after being unserialized. You must
                then call <methodname>getConnection()</methodname> yourself. You can make the
                adapter auto-reconnect by passing the
                <constant>Zend_Db::AUTO_RECONNECT_ON_UNSERIALIZE</constant> with
                <constant>TRUE</constant> as an adapter option.
            </para>

            <example id="zend.db.adapter.connecting.getconnection.example">
                <title>Handling Connection Exceptions</title>

                <programlisting language="php"><![CDATA[
try {
    $db = Zend_Db::factory('Pdo_Mysql', $parameters);
    $db->getConnection();
} catch (Zend_Db_Adapter_Exception $e) {
    // perhaps a failed login credential, or perhaps the RDBMS is not running
} catch (Zend_Exception $e) {
    // perhaps factory() failed to load the specified Adapter class
}
]]></programlisting>
            </example>
        </sect3>
    </sect2>

    <sect2 id="zend.db.adapter.example-database">
        <title>Example Database</title>

        <para>
            In the documentation for <classname>Zend_Db</classname> classes, we use a set of simple
            tables to illustrate usage of the classes and methods. These
            example tables could store information for tracking bugs in a
            software development project. The database contains four tables:
        </para>

        <itemizedlist>
            <listitem>
                <para>
                    <emphasis>accounts</emphasis> stores
                    information about each user of the bug-tracking database.
                </para>
            </listitem>

            <listitem>
                <para>
                    <emphasis>products</emphasis> stores
                    information about each product for which a bug can be
                    logged.
                </para>
            </listitem>

            <listitem>
                <para>
                    <emphasis>bugs</emphasis> stores information
                    about bugs, including that current state of the bug, the
                    person who reported the bug, the person who is assigned to
                    fix the bug, and the person who is assigned to verify the
                    fix.
                </para>
            </listitem>

            <listitem>
                <para>
                    <emphasis>bugs_products</emphasis> stores a
                    relationship between bugs and products. This implements a
                    many-to-many relationship, because a given bug may be
                    relevant to multiple products, and of course a given
                    product can have multiple bugs.
                </para>
            </listitem>
        </itemizedlist>

        <para>
            The following <acronym>SQL</acronym> data definition language pseudocode describes the
            tables in this example database. These example tables are used
            extensively by the automated unit tests for <classname>Zend_Db</classname>.
        </para>

        <programlisting language="sql"><![CDATA[
CREATE TABLE accounts (
  account_name      VARCHAR(100) NOT NULL PRIMARY KEY
);

CREATE TABLE products (
  product_id        INTEGER NOT NULL PRIMARY KEY,
  product_name      VARCHAR(100)
);

CREATE TABLE bugs (
  bug_id            INTEGER NOT NULL PRIMARY KEY,
  bug_description   VARCHAR(100),
  bug_status        VARCHAR(20),
  reported_by       VARCHAR(100) REFERENCES accounts(account_name),
  assigned_to       VARCHAR(100) REFERENCES accounts(account_name),
  verified_by       VARCHAR(100) REFERENCES accounts(account_name)
);

CREATE TABLE bugs_products (
  bug_id            INTEGER NOT NULL REFERENCES bugs,
  product_id        INTEGER NOT NULL REFERENCES products,
  PRIMARY KEY       (bug_id, product_id)
);
]]></programlisting>

        <para>
            Also notice that the 'bugs' table contains multiple
            foreign key references to the 'accounts' table.
            Each of these foreign keys may reference a different row in the
            'accounts' table for a given bug.
        </para>

        <para>
            The diagram below illustrates the physical data model of the
            example database.
        </para>

        <para>
            <inlinegraphic width="387" scale="100" align="center" valign="middle"
                fileref="figures/zend.db.adapter.example-database.png" format="PNG" />
        </para>
    </sect2>

    <sect2 id="zend.db.adapter.select">
        <title>Reading Query Results</title>

        <para>
            This section describes methods of the Adapter class with which you
            can run <acronym>SELECT</acronym> queries and retrieve the query results.
        </para>

        <sect3 id="zend.db.adapter.select.fetchall">
            <title>Fetching a Complete Result Set</title>

            <para>
                You can run a <acronym>SQL</acronym> <acronym>SELECT</acronym> query and retrieve
                its results in one step using the <methodname>fetchAll()</methodname> method.
            </para>

            <para>
                The first argument to this method is a string containing a
                <acronym>SELECT</acronym> statement. Alternatively, the first argument can be an
                object of class <link linkend="zend.db.select">Zend_Db_Select</link>.
                The Adapter automatically converts this object to a string
                representation of the <acronym>SELECT</acronym> statement.
            </para>

            <para>
                The second argument to <methodname>fetchAll()</methodname> is an array of
                values to substitute for parameter placeholders in the <acronym>SQL</acronym>
                statement.
            </para>

            <example id="zend.db.adapter.select.fetchall.example">
                <title>Using fetchAll()</title>

                <programlisting language="php"><![CDATA[
$sql = 'SELECT * FROM bugs WHERE bug_id = ?';

$result = $db->fetchAll($sql, 2);
]]></programlisting>
            </example>
        </sect3>

        <sect3 id="zend.db.adapter.select.fetch-mode">
            <title>Changing the Fetch Mode</title>

            <para>
                By default, <methodname>fetchAll()</methodname> returns an array of
                rows, each of which is an associative array. The keys of the
                associative array are the columns or column aliases named in
                the select query.
            </para>

            <para>
                You can specify a different style of fetching results using the
                <methodname>setFetchMode()</methodname> method. The modes supported are
                identified by constants:
            </para>

            <itemizedlist>
                <listitem>
                    <para>
                        <emphasis><constant>Zend_Db::FETCH_ASSOC</constant></emphasis>:
                        return data in an array of associative arrays.
                        The array keys are column names, as strings. This is the default fetch mode
                        for <classname>Zend_Db_Adapter</classname> classes.
                    </para>

                    <para>
                        Note that if your select-list contains more than one
                        column with the same name, for example if they are from
                        two different tables in a <acronym>JOIN</acronym>, there can be only one
                        entry in the associative array for a given name.
                        If you use the <constant>FETCH_ASSOC</constant> mode, you should specify
                        column aliases in your <acronym>SELECT</acronym> query to ensure that the
                        names result in unique array keys.
                    </para>

                    <para>
                        By default, these strings are returned as they are
                        returned by the database driver. This is typically the
                        spelling of the column in the <acronym>RDBMS</acronym> server. You can
                        specify the case for these strings, using the
                        <constant>Zend_Db::CASE_FOLDING</constant> option.
                        Specify this when instantiating the Adapter.
                        See <link linkend="zend.db.adapter.connecting.parameters.example1">this
                            example</link>
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <emphasis><constant>Zend_Db::FETCH_NUM</constant></emphasis>:
                        return data in an array of arrays. The arrays are
                        indexed by integers, corresponding to the position of
                        the respective field in the select-list of the query.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <emphasis><constant>Zend_Db::FETCH_BOTH</constant></emphasis>:
                        return data in an array of arrays. The array keys are
                        both strings as used in the <constant>FETCH_ASSOC</constant> mode, and
                        integers as used in the <constant>FETCH_NUM</constant> mode. Note that the
                        number of elements in the array is double that which
                        would be in the array if you used either <constant>FETCH_ASSOC</constant>
                        or <constant>FETCH_NUM</constant>.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <emphasis><constant>Zend_Db::FETCH_COLUMN</constant></emphasis>:
                        return data in an array of values. The value in each array
                        is the value returned by one column of the result set.
                        By default, this is the first column, indexed by 0.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <emphasis><constant>Zend_Db::FETCH_OBJ</constant></emphasis>:
                        return data in an array of objects. The default class
                        is the <acronym>PHP</acronym> built-in class stdClass. Columns of the
                        result set are available as public properties of the
                        object.
                    </para>
                </listitem>
            </itemizedlist>

            <example id="zend.db.adapter.select.fetch-mode.example">
                <title>Using setFetchMode()</title>

                <programlisting language="php"><![CDATA[
$db->setFetchMode(Zend_Db::FETCH_OBJ);

$result = $db->fetchAll('SELECT * FROM bugs WHERE bug_id = ?', 2);

// $result is an array of objects
echo $result[0]->bug_description;
]]></programlisting>
            </example>
        </sect3>

        <sect3 id="zend.db.adapter.select.fetchassoc">
            <title>Fetching a Result Set as an Associative Array</title>

            <para>
                The <methodname>fetchAssoc()</methodname> method returns data in an array
                of associative arrays, regardless of what value you have set
                for the fetch mode, using the first column as the array index.
            </para>

            <example id="zend.db.adapter.select.fetchassoc.example">
                <title>Using fetchAssoc()</title>

                <programlisting language="php"><![CDATA[
$db->setFetchMode(Zend_Db::FETCH_OBJ);

$result = $db->fetchAssoc(
    'SELECT bug_id, bug_description, bug_status FROM bugs'
);

// $result is an array of associative arrays, in spite of the fetch mode
echo $result[2]['bug_description']; // Description of Bug #2
echo $result[1]['bug_description']; // Description of Bug #1
]]></programlisting>
            </example>
        </sect3>

        <sect3 id="zend.db.adapter.select.fetchcol">
            <title>Fetching a Single Column from a Result Set</title>

            <para>
                The <methodname>fetchCol()</methodname> method returns data in an array
                of values, regardless of the value you have set for the fetch mode.
                This only returns the first column returned by the query.
                Any other columns returned by the query are discarded.
                If you need to return a column other than the first, see
                <link linkend="zend.db.statement.fetching.fetchcolumn">this section</link>.
            </para>

            <example id="zend.db.adapter.select.fetchcol.example">
                <title>Using fetchCol()</title>

                <programlisting language="php"><![CDATA[
$db->setFetchMode(Zend_Db::FETCH_OBJ);

$result = $db->fetchCol(
    'SELECT bug_description, bug_id FROM bugs WHERE bug_id = ?', 2);

// contains bug_description; bug_id is not returned
echo $result[0];
]]></programlisting>
            </example>
        </sect3>

        <sect3 id="zend.db.adapter.select.fetchpairs">
            <title>Fetching Key-Value Pairs from a Result Set</title>

            <para>
                The <methodname>fetchPairs()</methodname> method returns data in an array
                of key-value pairs, as an associative array with a single entry
                per row. The key of this associative array is taken from the
                first column returned by the <acronym>SELECT</acronym> query. The value is taken
                from the second column returned by the <acronym>SELECT</acronym> query. Any other
                columns returned by the query are discarded.
            </para>

            <para>
                You should design the <acronym>SELECT</acronym> query so that the first column
                returned has unique values. If there are duplicates values in
                the first column, entries in the associative array will be
                overwritten.
            </para>

            <example id="zend.db.adapter.select.fetchpairs.example">
                <title>Using fetchPairs()</title>

                <programlisting language="php"><![CDATA[
$db->setFetchMode(Zend_Db::FETCH_OBJ);

$result = $db->fetchPairs('SELECT bug_id, bug_status FROM bugs');

echo $result[2];
]]></programlisting>
            </example>
        </sect3>

        <sect3 id="zend.db.adapter.select.fetchrow">
            <title>Fetching a Single Row from a Result Set</title>

            <para>
                The <methodname>fetchRow()</methodname> method returns data using the
                current fetch mode, but it returns only the first row
                fetched from the result set.
            </para>

            <example id="zend.db.adapter.select.fetchrow.example">
                <title>Using fetchRow()</title>

                <programlisting language="php"><![CDATA[
$db->setFetchMode(Zend_Db::FETCH_OBJ);

$result = $db->fetchRow('SELECT * FROM bugs WHERE bug_id = 2');

// note that $result is a single object, not an array of objects
echo $result->bug_description;
]]></programlisting>
            </example>
        </sect3>

        <sect3 id="zend.db.adapter.select.fetchone">
            <title>Fetching a Single Scalar from a Result Set</title>

            <para>
                The <methodname>fetchOne()</methodname> method is like a combination
                of <methodname>fetchRow()</methodname> with <methodname>fetchCol()</methodname>,
                in that it returns data only for the first row fetched from
                the result set, and it returns only the value of the first
                column in that row. Therefore it returns only a single
                scalar value, not an array or an object.
            </para>

            <example id="zend.db.adapter.select.fetchone.example">
                <title>Using fetchOne()</title>

                <programlisting language="php"><![CDATA[
$result = $db->fetchOne('SELECT bug_status FROM bugs WHERE bug_id = 2');

// this is a single string value
echo $result;
]]></programlisting>
            </example>
        </sect3>
    </sect2>

    <sect2 id="zend.db.adapter.write">
        <title>Writing Changes to the Database</title>

        <para>
            You can use the Adapter class to write new data or change existing
            data in your database. This section describes methods to do these
            operations.
        </para>

        <sect3 id="zend.db.adapter.write.insert">
            <title>Inserting Data</title>

            <para>
                You can add new rows to a table in your database using the
                <methodname>insert()</methodname> method. The first argument is a string
                that names the table, and the second argument is an associative
                array, mapping column names to data values.
            </para>

            <example id="zend.db.adapter.write.insert.example">
                <title>Inserting in a Table</title>

                <programlisting language="php"><![CDATA[
$data = array(
    'created_on'      => '2007-03-22',
    'bug_description' => 'Something wrong',
    'bug_status'      => 'NEW'
);

$db->insert('bugs', $data);
]]></programlisting>
            </example>

            <para>
                Columns you exclude from the array of data are not specified to
                the database. Therefore, they follow the same rules that an
                <acronym>SQL</acronym> <acronym>INSERT</acronym> statement follows: if the column
                has a <acronym>DEFAULT</acronym> clause, the column takes that value in the row
                created, otherwise the column is left in a <constant>NULL</constant> state.
            </para>

            <para>
                By default, the values in your data array are inserted using
                parameters. This reduces risk of some types of security
                issues. You don't need to apply escaping or quoting to values
                in the data array.
            </para>

            <para>
                You might need values in the data array to be treated as <acronym>SQL</acronym>
                expressions, in which case they should not be quoted. By
                default, all data values passed as strings are treated as
                string literals. To specify that the value is an <acronym>SQL</acronym>
                expression and therefore should not be quoted, pass the value
                in the data array as an object of type <classname>Zend_Db_Expr</classname> instead
                of a plain string.
            </para>

            <example id="zend.db.adapter.write.insert.example2">
                <title>Inserting Expressions in a Table</title>

                <programlisting language="php"><![CDATA[
$data = array(
    'created_on'      => new Zend_Db_Expr('CURDATE()'),
    'bug_description' => 'Something wrong',
    'bug_status'      => 'NEW'
);

$db->insert('bugs', $data);
]]></programlisting>
            </example>
        </sect3>

        <sect3 id="zend.db.adapter.write.lastinsertid">
            <title>Retrieving a Generated Value</title>

            <para>
                Some <acronym>RDBMS</acronym> brands support auto-incrementing primary keys.
                A table defined this way generates a primary key value
                automatically during an <acronym>INSERT</acronym> of a new row. The return value
                of the <methodname>insert()</methodname> method is <emphasis>not</emphasis>
                the last inserted ID, because the table might not have an
                auto-incremented column. Instead, the return value is the
                number of rows affected (usually 1).
            </para>

            <para>
                If your table is defined with an auto-incrementing primary key,
                you can call the <methodname>lastInsertId()</methodname> method after the
                insert. This method returns the last value generated in the
                scope of the current database connection.
            </para>

            <example id="zend.db.adapter.write.lastinsertid.example-1">
                <title>Using lastInsertId() for an Auto-Increment Key</title>

                <programlisting language="php"><![CDATA[
$db->insert('bugs', $data);

// return the last value generated by an auto-increment column
$id = $db->lastInsertId();
]]></programlisting>
            </example>

            <para>
                Some <acronym>RDBMS</acronym> brands support a sequence object, which generates
                unique values to serve as primary key values. To support
                sequences, the <methodname>lastInsertId()</methodname> method accepts two
                optional string arguments. These arguments name the table and
                the column, assuming you have followed the convention that a
                sequence is named using the table and column names for which
                the sequence generates values, and a suffix "_seq". This is
                based on the convention used by PostgreSQL when naming
                sequences for <constant>SERIAL</constant> columns. For example, a table "bugs" with
                primary key column "bug_id" would use a sequence named
                "bugs_bug_id_seq".
            </para>

            <example id="zend.db.adapter.write.lastinsertid.example-2">
                <title>Using lastInsertId() for a Sequence</title>

                <programlisting language="php"><![CDATA[
$db->insert('bugs', $data);

// return the last value generated by sequence 'bugs_bug_id_seq'.
$id = $db->lastInsertId('bugs', 'bug_id');

// alternatively, return the last value generated by sequence 'bugs_seq'.
$id = $db->lastInsertId('bugs');
]]></programlisting>
            </example>

            <para>
                If the name of your sequence object does not follow this naming
                convention, use the <methodname>lastSequenceId()</methodname> method
                instead. This method takes a single string argument, naming
                the sequence literally.
            </para>

            <example id="zend.db.adapter.write.lastinsertid.example-3">
                <title>Using lastSequenceId()</title>

                <programlisting language="php"><![CDATA[
$db->insert('bugs', $data);

// return the last value generated by sequence 'bugs_id_gen'.
$id = $db->lastSequenceId('bugs_id_gen');
]]></programlisting>
            </example>

            <para>
                For <acronym>RDBMS</acronym> brands that don't support sequences, including MariaDB,
        MySQL, Microsoft <acronym>SQL</acronym> Server, and SQLite, the arguments to the
                <methodname>lastInsertId()</methodname> method are ignored, and the value returned
                is the most recent value generated for any table by <acronym>INSERT</acronym>
                operations during the current connection. For these <acronym>RDBMS</acronym> brands,
                the <methodname>lastSequenceId()</methodname> method always returns
                <constant>NULL</constant>.
            </para>

            <note>
                <title>Why Not Use "SELECT MAX(id) FROM table"?</title>

                <para>
                    Sometimes this query returns the most recent primary key
                    value inserted into the table. However, this technique
                    is not safe to use in an environment where multiple clients are
                    inserting records to the database. It is possible, and
                    therefore is bound to happen eventually, that another
                    client inserts another row in the instant between the
                    insert performed by your client application and your query
                    for the <methodname>MAX(id)</methodname> value. Thus the value returned does
                    not identify the row you inserted, it identifies the row
                    inserted by some other client. There is no way to know
                    when this has happened.
                </para>

                <para>
                    Using a strong transaction isolation mode such as
                    "repeatable read" can mitigate this risk, but some <acronym>RDBMS</acronym>
                    brands don't support the transaction isolation required for
                    this, or else your application may use a lower transaction
                    isolation mode by design.
                </para>

                <para>
                    Furthermore, using an expression like "<command>MAX(id)+1</command>" to generate
                    a new value for a primary key is not safe, because two clients
                    could do this query simultaneously, and then both use the same
                    calculated value for their next <acronym>INSERT</acronym> operation.
                </para>

                <para>
                    All <acronym>RDBMS</acronym> brands provide mechanisms to generate unique
                    values, and to return the last value generated. These
                    mechanisms necessarily work outside of the scope of
                    transaction isolation, so there is no chance of two clients
                    generating the same value, and there is no chance that the
                    value generated by another client could be reported to your
                    client's connection as the last value generated.
                </para>
            </note>
        </sect3>

        <sect3 id="zend.db.adapter.write.update">
            <title>Updating Data</title>

            <para>
                You can update rows in a database table using the
                <methodname>update()</methodname> method of an Adapter. This method takes
                three arguments: the first is the name of the table; the
                second is an associative array mapping columns to change to new
                values to assign to these columns.
            </para>

            <para>
                The values in the data array are treated as string literals.
                See <link linkend="zend.db.adapter.write.insert">this section</link>
                for information on using <acronym>SQL</acronym> expressions in the data array.
            </para>

            <para>
                The third argument is a string containing an <acronym>SQL</acronym> expression
                that is used as criteria for the rows to change. The values
                and identifiers in this argument are not quoted or escaped.
                You are responsible for ensuring that any dynamic content is
                interpolated into this string safely.
                See <link linkend="zend.db.adapter.quoting">this section</link>
                for methods to help you do this.
            </para>

            <para>
                The return value is the number of rows affected by the update
                operation.
            </para>

            <example id="zend.db.adapter.write.update.example">
                <title>Updating Rows</title>

                <programlisting language="php"><![CDATA[
$data = array(
    'updated_on'      => '2007-03-23',
    'bug_status'      => 'FIXED'
);

$n = $db->update('bugs', $data, 'bug_id = 2');
]]></programlisting>
            </example>

            <para>
                If you omit the third argument, then all rows in the database
                table are updated with the values specified in the data array.
            </para>

            <para>
                If you provide an array of strings as the third argument, these
                strings are joined together as terms in an expression separated
                by <constant>AND</constant> operators.
            </para>

            <para>
                If you provide an array of arrays as the third argument, the
                values will be automatically quoted into the keys. These
                will then be joined together as terms, separated by
                <constant>AND</constant> operators.
            </para>

            <example id="zend.db.adapter.write.update.example-array">
                <title>Updating Rows Using an Array of Expressions</title>

                <programlisting language="php"><![CDATA[
$data = array(
    'updated_on'      => '2007-03-23',
    'bug_status'      => 'FIXED'
);

$where[] = "reported_by = 'goofy'";
$where[] = "bug_status = 'OPEN'";

$n = $db->update('bugs', $data, $where);

// Resulting SQL is:
//  UPDATE "bugs" SET "update_on" = '2007-03-23', "bug_status" = 'FIXED'
//  WHERE ("reported_by" = 'goofy') AND ("bug_status" = 'OPEN')
]]></programlisting>
            </example>

            <example id="zend.db.adapter.write.update.example-arrayofarrays">
                <title>Updating Rows Using an Array of Arrays</title>

                <programlisting language="php"><![CDATA[
$data = array(
    'updated_on'      => '2007-03-23',
    'bug_status'      => 'FIXED'
);

$where['reported_by = ?'] = 'goofy';
$where['bug_status = ?']  = 'OPEN';

$n = $db->update('bugs', $data, $where);

// Resulting SQL is:
//  UPDATE "bugs" SET "update_on" = '2007-03-23', "bug_status" = 'FIXED'
//  WHERE ("reported_by" = 'goofy') AND ("bug_status" = 'OPEN')
]]></programlisting>
            </example>
        </sect3>

        <sect3 id="zend.db.adapter.write.delete">
            <title>Deleting Data</title>

            <para>
                You can delete rows from a database table using the
                <methodname>delete()</methodname> method. This method takes two arguments:
                the first is a string naming the table.
            </para>

            <para>
                The second argument is a string containing an <acronym>SQL</acronym> expression
                that is used as criteria for the rows to delete. The values
                and identifiers in this argument are not quoted or escaped.
                You are responsible for ensuring that any dynamic content is
                interpolated into this string safely.
                See <link linkend="zend.db.adapter.quoting"> this section</link>
                for methods to help you do this.
            </para>

            <para>
                The return value is the number of rows affected by the delete
                operation.
            </para>

            <example id="zend.db.adapter.write.delete.example">
                <title>Deleting Rows</title>

                <programlisting language="php"><![CDATA[
$n = $db->delete('bugs', 'bug_id = 3');
]]></programlisting>
            </example>

            <para>
                If you omit the second argument, the result is that all rows in
                the database table are deleted.
            </para>

            <para>
                If you provide an array of strings as the second argument, these
                strings are joined together as terms in an expression separated
                by <constant>AND</constant> operators.
            </para>

            <para>
                If you provide an array of arrays as the second argument, the
                values will be automatically quoted into the keys. These
                will then be joined together as terms, separated by
                <constant>AND</constant> operators.
            </para>
        </sect3>
    </sect2>

    <sect2 id="zend.db.adapter.quoting">
        <title>Quoting Values and Identifiers</title>

        <para>
            When you form <acronym>SQL</acronym> queries, often it is the case that you need to
            include the values of <acronym>PHP</acronym> variables in <acronym>SQL</acronym>
            expressions. This is risky, because if the value in a <acronym>PHP</acronym> string
            contains certain symbols, such as the quote symbol, it could result in invalid
            <acronym>SQL</acronym>. For example, notice the imbalanced quote characters in the
            following query:
        </para>

        <programlisting language="php"><![CDATA[
$name = "O'Reilly";
$sql = "SELECT * FROM bugs WHERE reported_by = '$name'";

echo $sql;
// SELECT * FROM bugs WHERE reported_by = 'O'Reilly'
]]></programlisting>

        <para>
            Even worse is the risk that such code mistakes might be exploited
            deliberately by a person who is trying to manipulate the function
            of your web application. If they can specify the value of a <acronym>PHP</acronym>
            variable through the use of an <acronym>HTTP</acronym> parameter or other mechanism,
            they might be able to make your <acronym>SQL</acronym> queries do things that you
            didn't intend them to do, such as return data to which the person
            should not have privilege to read. This is a serious and widespread
            technique for violating application security, known as "SQL Injection" (see <ulink
                url="http://en.wikipedia.org/wiki/SQL_Injection">http://en.wikipedia.org/wiki/SQL_Injection</ulink>).
        </para>

        <para>
            The <classname>Zend_Db</classname> Adapter class provides convenient functions to help
            you reduce vulnerabilities to <acronym>SQL</acronym> Injection attacks in your
            <acronym>PHP</acronym> code. The solution is to escape special characters such as quotes
            in <acronym>PHP</acronym> values before they are interpolated into your
            <acronym>SQL</acronym> strings. This protects against both accidental and deliberate
            manipulation of <acronym>SQL</acronym> strings by <acronym>PHP</acronym> variables that
            contain special characters.
        </para>

        <sect3 id="zend.db.adapter.quoting.quote">
            <title>Using quote()</title>

            <para>
                The <methodname>quote()</methodname> method accepts a single argument, a
                scalar string value. It returns the value with special
                characters escaped in a manner appropriate for the <acronym>RDBMS</acronym> you
                are using, and surrounded by string value delimiters. The
                standard <acronym>SQL</acronym> string value delimiter is the single-quote
                (').
            </para>

            <example id="zend.db.adapter.quoting.quote.example">
                <title>Using quote()</title>

                <programlisting language="php"><![CDATA[
$name = $db->quote("O'Reilly");
echo $name;
// 'O\'Reilly'

$sql = "SELECT * FROM bugs WHERE reported_by = $name";

echo $sql;
// SELECT * FROM bugs WHERE reported_by = 'O\'Reilly'
]]></programlisting>
            </example>

            <para>
                Note that the return value of <methodname>quote()</methodname> includes the
                quote delimiters around the string. This is different from
                some functions that escape special characters but do not add
                the quote delimiters, for example <ulink
                    url="http://www.php.net/mysqli_real_escape_string">mysql_real_escape_string()</ulink>.
            </para>

            <para>
                Values may need to be quoted or not quoted according to the <acronym>SQL</acronym>
                datatype context in which they are used. For instance, in some
                <acronym>RDBMS</acronym> brands, an integer value must not be quoted as a string
                if it is compared to an integer-type column or expression.
                In other words, the following is an error in some <acronym>SQL</acronym>
                implementations, assuming <property>intColumn</property> has a
                <acronym>SQL</acronym> datatype of <constant>INTEGER</constant>
            </para>

            <programlisting language="php"><![CDATA[
SELECT * FROM atable WHERE intColumn = '123'
]]></programlisting>

            <para>
                You can use the optional second argument to the
                <methodname>quote()</methodname> method to apply quoting selectively for
                the <acronym>SQL</acronym> datatype you specify.
            </para>

            <example id="zend.db.adapter.quoting.quote.example-2">
                <title>Using quote() with a SQL Type</title>

                <programlisting language="php"><![CDATA[
$value = '1234';
$sql = 'SELECT * FROM atable WHERE intColumn = '
     . $db->quote($value, 'INTEGER');
]]></programlisting>
            </example>

            <para>
                Each <classname>Zend_Db_Adapter</classname> class has encoded the names of numeric
                <acronym>SQL</acronym> datatypes for the respective brand of
                <acronym>RDBMS</acronym>. You can also use the constants
                <constant>Zend_Db::INT_TYPE</constant>, <constant>Zend_Db::BIGINT_TYPE</constant>,
                and <constant>Zend_Db::FLOAT_TYPE</constant> to write code in a more
                <acronym>RDBMS</acronym>-independent way.
            </para>

            <para>
                <classname>Zend_Db_Table</classname> specifies <acronym>SQL</acronym> types to
                <methodname>quote()</methodname> automatically when generating
                <acronym>SQL</acronym> queries that reference a table's key columns.
            </para>
        </sect3>

        <sect3 id="zend.db.adapter.quoting.quote-into">
            <title>Using quoteInto()</title>

            <para>
                The most typical usage of quoting is to interpolate a <acronym>PHP</acronym>
                variable into a <acronym>SQL</acronym> expression or statement. You can use the
                <methodname>quoteInto()</methodname> method to do this in one step. This
                method takes two arguments: the first argument is a string
                containing a placeholder symbol (?), and the
                second argument is a value or <acronym>PHP</acronym> variable that should be
                substituted for that placeholder.
            </para>

            <para>
                The placeholder symbol is the same symbol used by many <acronym>RDBMS</acronym>
                brands for positional parameters, but the
                <methodname>quoteInto()</methodname> method only emulates query parameters.
                The method simply interpolates the value into the string,
                escapes special characters, and applies quotes around it.
                True query parameters maintain the separation between the <acronym>SQL</acronym>
                string and the parameters as the statement is parsed in the
                <acronym>RDBMS</acronym> server.
            </para>

            <example id="zend.db.adapter.quoting.quote-into.example">
                <title>Using quoteInto()</title>

                <programlisting language="php"><![CDATA[
$sql = $db->quoteInto("SELECT * FROM bugs WHERE reported_by = ?", "O'Reilly");

echo $sql;
// SELECT * FROM bugs WHERE reported_by = 'O\'Reilly'
]]></programlisting>
            </example>

            <para>
                You can use the optional third parameter of
                <methodname>quoteInto()</methodname> to specify the <acronym>SQL</acronym> datatype.
                Numeric datatypes are not quoted, and other types are quoted.
            </para>

            <example id="zend.db.adapter.quoting.quote-into.example-2">
                <title>Using quoteInto() with a SQL Type</title>

                <programlisting language="php"><![CDATA[
$sql = $db
    ->quoteInto("SELECT * FROM bugs WHERE bug_id = ?", '1234', 'INTEGER');

echo $sql;
// SELECT * FROM bugs WHERE reported_by = 1234
]]></programlisting>
            </example>
        </sect3>

        <sect3 id="zend.db.adapter.quoting.quote-identifier">
            <title>Using quoteIdentifier()</title>

            <para>
                Values are not the only part of <acronym>SQL</acronym> syntax that might need to
                be variable. If you use <acronym>PHP</acronym> variables to name tables, columns,
                or other identifiers in your <acronym>SQL</acronym> statements, you might need to
                quote these strings too. By default, <acronym>SQL</acronym> identifiers have
                syntax rules like <acronym>PHP</acronym> and most other programming languages.
                For example, identifiers should not contain spaces, certain
                punctuation or special characters, or international characters.
                Also certain words are reserved for <acronym>SQL</acronym> syntax, and should not
                be used as identifiers.
            </para>

            <para>
                However, <acronym>SQL</acronym> has a feature called
                <emphasis>delimited identifiers</emphasis>, which allows broader choices for the
                spelling of identifiers. If you enclose a <acronym>SQL</acronym> identifier in the
                proper types of quotes, you can use identifiers with spellings that would be invalid
                without the quotes. Delimited identifiers can contain spaces,
                punctuation, or international characters. You can also use <acronym>SQL</acronym>
                reserved words if you enclose them in identifier delimiters.
            </para>

            <para>
                The <methodname>quoteIdentifier()</methodname> method works like
                <methodname>quote()</methodname>, but it applies the identifier delimiter
                characters to the string according to the type of Adapter you
                use. For example, standard <acronym>SQL</acronym> uses double-quotes
                (") for identifier delimiters, and most <acronym>RDBMS</acronym>
                brands use that symbol. MySQL uses back-quotes (`) by default. The
                <methodname>quoteIdentifier()</methodname> method also escapes special
                characters within the string argument.
            </para>

            <example id="zend.db.adapter.quoting.quote-identifier.example">
                <title>Using quoteIdentifier()</title>

                <programlisting language="php"><![CDATA[
// we might have a table name that is an SQL reserved word
$tableName = $db->quoteIdentifier("order");

$sql = "SELECT * FROM $tableName";

echo $sql
// SELECT * FROM "order"
]]></programlisting>
            </example>

            <para>
                <acronym>SQL</acronym> delimited identifiers are case-sensitive, unlike unquoted
                identifiers. Therefore, if you use delimited identifiers, you
                must use the spelling of the identifier exactly as it is stored
                in your schema, including the case of the letters.
            </para>

            <para>
                In most cases where <acronym>SQL</acronym> is generated within
                <classname>Zend_Db</classname> classes, the default is that all identifiers are
                delimited automatically. You can change this behavior with the option
                <constant>Zend_Db::AUTO_QUOTE_IDENTIFIERS</constant>. Specify this
                when instantiating the Adapter.
                See <link linkend="zend.db.adapter.connecting.parameters.example2">this
                    example</link>.
            </para>
        </sect3>
    </sect2>

    <sect2 id="zend.db.adapter.transactions">
        <title>Controlling Database Transactions</title>

        <para>
            Databases define transactions as logical units of work that can be
            committed or rolled back as a single change, even if they operate
            on multiple tables. All queries to a database are executed within
            the context of a transaction, even if the database driver manages
            them implicitly. This is called <emphasis>auto-commit</emphasis>
            mode, in which the database driver creates a transaction for every
            statement you execute, and commits that transaction after your
            <acronym>SQL</acronym> statement has been executed. By default, all
            <classname>Zend_Db</classname> Adapter classes operate in auto-commit mode.
        </para>

        <para>
            Alternatively, you can specify the beginning and resolution of a
            transaction, and thus control how many <acronym>SQL</acronym> queries are included in
            a single group that is committed (or rolled back) as a single
            operation. Use the <methodname>beginTransaction()</methodname> method to
            initiate a transaction. Subsequent <acronym>SQL</acronym> statements are executed in
            the context of the same transaction until you resolve it
            explicitly.
        </para>

        <para>
            To resolve the transaction, use either the <methodname>commit()</methodname> or
            <methodname>rollBack()</methodname> methods. The <methodname>commit()</methodname>
            method marks changes made during your transaction as committed, which
            means the effects of these changes are shown in queries run in
            other transactions.
        </para>

        <para>
            The <methodname>rollBack()</methodname> method does the opposite: it discards
            the changes made during your transaction. The changes are
            effectively undone, and the state of the data returns to how it was
            before you began your transaction. However, rolling back your
            transaction has no effect on changes made by other transactions
            running concurrently.
        </para>

        <para>
            After you resolve this transaction, <classname>Zend_Db_Adapter</classname>
            returns to auto-commit mode until you call
            <methodname>beginTransaction()</methodname> again.
        </para>

        <example id="zend.db.adapter.transactions.example">
            <title>Managing a Transaction to Ensure Consistency</title>

            <programlisting language="php"><![CDATA[
// Start a transaction explicitly.
$db->beginTransaction();

try {
    // Attempt to execute one or more queries:
    $db->query(...);
    $db->query(...);
    $db->query(...);

    // If all succeed, commit the transaction and all changes
    // are committed at once.
    $db->commit();

} catch (Exception $e) {
    // If any of the queries failed and threw an exception,
    // we want to roll back the whole transaction, reversing
    // changes made in the transaction, even those that succeeded.
    // Thus all changes are committed together, or none are.
    $db->rollBack();
    echo $e->getMessage();
}
]]></programlisting>
        </example>
    </sect2>

    <sect2 id="zend.db.adapter.list-describe">
        <title>Listing and Describing Tables</title>

        <para>
            The <methodname>listTables()</methodname> method returns an array of strings,
            naming all tables in the current database.
        </para>

        <para>
            The <methodname>describeTable()</methodname> method returns an associative
            array of metadata about a table. Specify the name of the table
            as a string in the first argument to this method. The second
            argument is optional, and names the schema in which the table
            exists.
        </para>

        <para>
            The keys of the associative array returned are the column names of
            the table. The value corresponding to each column is also an
            associative array, with the following keys and values:
        </para>

        <table frame="all" cellpadding="5" id="zend.db.adapter.list-describe.metadata">
            <title>Metadata Fields Returned by describeTable()</title>

            <tgroup cols="3" align="left" colsep="1" rowsep="1">
                <thead>
                    <row>
                        <entry>Key</entry>
                        <entry>Type</entry>
                        <entry>Description</entry>
                    </row>
                </thead>

                <tbody>
                    <row>
                        <entry><constant>SCHEMA_NAME</constant></entry>
                        <entry>(string)</entry>
                        <entry>Name of the database schema in which this table exists.</entry>
                    </row>

                    <row>
                        <entry><constant>TABLE_NAME</constant></entry>
                        <entry>(string)</entry>
                        <entry>Name of the table to which this column belongs.</entry>
                    </row>

                    <row>
                        <entry><constant>COLUMN_NAME</constant></entry>
                        <entry>(string)</entry>
                        <entry>Name of the column.</entry>
                    </row>

                    <row>
                        <entry><constant>COLUMN_POSITION</constant></entry>
                        <entry>(integer)</entry>
                        <entry>Ordinal position of the column in the table.</entry>
                    </row>

                    <row>
                        <entry><constant>DATA_TYPE</constant></entry>
                        <entry>(string)</entry>
                        <entry><acronym>RDBMS</acronym> name of the datatype of the column.</entry>
                    </row>

                    <row>
                        <entry><constant>DEFAULT</constant></entry>
                        <entry>(string)</entry>
                        <entry>Default value for the column, if any.</entry>
                    </row>

                    <row>
                        <entry><constant>NULLABLE</constant></entry>
                        <entry>(boolean)</entry>

                        <entry>
                            <constant>TRUE</constant> if the column accepts <acronym>SQL</acronym>
                            <constant>NULL</constant>'s, <constant>FALSE</constant> if the
                            column has a <constant>NOT</constant> <constant>NULL</constant>
                            constraint.
                        </entry>
                    </row>

                    <row>
                        <entry><constant>LENGTH</constant></entry>
                        <entry>(integer)</entry>

                        <entry>
                            Length or size of the column as reported by the
                            <acronym>RDBMS</acronym>.
                        </entry>
                    </row>

                    <row>
                        <entry><constant>SCALE</constant></entry>
                        <entry>(integer)</entry>

                        <entry>
                            Scale of <acronym>SQL</acronym> <constant>NUMERIC</constant> or
                            <constant>DECIMAL</constant> type.
                        </entry>
                    </row>

                    <row>
                        <entry><constant>PRECISION</constant></entry>
                        <entry>(integer)</entry>

                        <entry>
                            Precision of <acronym>SQL</acronym> <constant>NUMERIC</constant> or
                            <constant>DECIMAL</constant> type.
                        </entry>
                    </row>

                    <row>
                        <entry><constant>UNSIGNED</constant></entry>
                        <entry>(boolean)</entry>

                        <entry>
                            <constant>TRUE</constant> if an integer-based type is reported as
                            <constant>UNSIGNED</constant>.
                        </entry>
                    </row>

                    <row>
                        <entry><constant>PRIMARY</constant></entry>
                        <entry>(boolean)</entry>

                        <entry>
                            <constant>TRUE</constant> if the column is part of the primary key of
                            this table.
                        </entry>
                    </row>

                    <row>
                        <entry><constant>PRIMARY_POSITION</constant></entry>
                        <entry>(integer)</entry>
                        <entry>Ordinal position (1-based) of the column in the primary key.</entry>
                    </row>

                    <row>
                        <entry><constant>IDENTITY</constant></entry>
                        <entry>(boolean)</entry>

                        <entry>
                            <constant>TRUE</constant> if the column uses an auto-generated value.
                        </entry>
                    </row>
                </tbody>
            </tgroup>
        </table>

        <note>
            <title>How the IDENTITY Metadata Field Relates to Specific RDBMSs</title>

            <para>
                The <constant>IDENTITY</constant> metadata field was chosen as an 'idiomatic' term
                to represent a relation to surrogate keys. This field can be
                commonly known by the following values:-
            </para>

            <itemizedlist>
                <listitem>
                    <para>
                        <constant>IDENTITY</constant> - <acronym>DB2</acronym>,
                        <acronym>MSSQL</acronym>
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <constant>AUTO_INCREMENT</constant> - MySQL/MariaDB
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <constant>SERIAL</constant> - PostgreSQL
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <constant>SEQUENCE</constant> - Oracle
                    </para>
                </listitem>
            </itemizedlist>
        </note>

        <para>
            If no table exists matching the table name and optional schema name
            specified, then <methodname>describeTable()</methodname> returns an empty array.
        </para>
    </sect2>

    <sect2 id="zend.db.adapter.closing">
        <title>Closing a Connection</title>

        <para>
            Normally it is not necessary to close a database connection. <acronym>PHP</acronym>
            automatically cleans up all resources and the end of a request.
            Database extensions are designed to close the connection as the
            reference to the resource object is cleaned up.
        </para>

        <para>
            However, if you have a long-duration <acronym>PHP</acronym> script that initiates many
            database connections, you might need to close the connection, to avoid
            exhausting the capacity of your <acronym>RDBMS</acronym> server. You can use the
            Adapter's <methodname>closeConnection()</methodname> method to explicitly close
            the underlying database connection.
        </para>

        <para>
            Since release 1.7.2, you could check you are currently connected to the
            <acronym>RDBMS</acronym> server with the method <methodname>isConnected()</methodname>.
            This means that a connection resource has been initiated and wasn't closed. This
            function is not currently able to test for example a server side closing of the
            connection. This is internally use to close the connection. It allow you to close the
            connection multiple times without errors. It was already the case before 1.7.2 for
            <acronym>PDO</acronym> adapters but not for the others.
        </para>

        <example id="zend.db.adapter.closing.example">
            <title>Closing a Database Connection</title>

            <programlisting language="php"><![CDATA[
$db->closeConnection();
]]></programlisting>
        </example>

        <note>
            <title>Does Zend_Db Support Persistent Connections?</title>

            <para>
                Yes, persistence is supported through the addition of
                the <property>persistent</property> flag set to <constant>TRUE</constant> in the
                configuration (not driver_configuration) of an adapter
                in <classname>Zend_Db</classname>.
            </para>

            <example id="zend.db.adapter.connecting.persistence.example">
                <title>Using the Persitence Flag with the Oracle Adapter</title>

                <programlisting language="php"><![CDATA[
$db = Zend_Db::factory('Oracle', array(
    'host'       => '127.0.0.1',
    'username'   => 'webuser',
    'password'   => 'xxxxxxxx',
    'dbname'     => 'test',
    'persistent' => true
));
]]></programlisting>
            </example>

            <para>
                Please note that using persistent connections can cause an
                excess of idle connections on the <acronym>RDBMS</acronym> server, which causes
                more problems than any performance gain you might achieve by
                reducing the overhead of making connections.
            </para>

            <para>
                Database connections have state. That is, some objects in the
                <acronym>RDBMS</acronym> server exist in session scope. Examples are locks, user
                variables, temporary tables, and information about the most
                recently executed query, such as rows affected, and last
                generated id value. If you use persistent connections, your
                application could access invalid or privileged data that were
                created in a previous <acronym>PHP</acronym> request.
            </para>

            <para>
                Currently, only Oracle, <acronym>DB2</acronym>, and the <acronym>PDO</acronym>
                adapters (where specified by <acronym>PHP</acronym>) support persistence in
                <classname>Zend_Db</classname>.
            </para>
        </note>
    </sect2>

    <sect2 id="zend.db.adapter.other-statements">
        <title>Running Other Database Statements</title>

        <para>
            There might be cases in which you need to access the connection
            object directly, as provided by the <acronym>PHP</acronym> database extension. Some
            of these extensions may offer features that are not surfaced by
            methods of <classname>Zend_Db_Adapter_Abstract</classname>.
        </para>

        <para>
            For example, all <acronym>SQL</acronym> statements run by <classname>Zend_Db</classname>
            are prepared, then executed. However, some database features are incompatible with
            prepared statements. <constant>DDL</constant> statements like
            <constant>CREATE</constant> and <constant>ALTER</constant> cannot be prepared in MySQL.
            Also, <acronym>SQL</acronym> statements don't benefit from the <ulink
                url="http://dev.mysql.com/doc/refman/5.1/en/query-cache-how.html">MySQL Query
                Cache</ulink>, prior to MySQL 5.1.17.
        </para>

        <para>
            Most <acronym>PHP</acronym> database extensions provide a method to execute
            <acronym>SQL</acronym> statements without preparing them. For example, in
            <acronym>PDO</acronym>, this method is <methodname>exec()</methodname>. You can access
            the connection object in the <acronym>PHP</acronym> extension directly using
            <methodname>getConnection()</methodname>.
        </para>

        <example id="zend.db.adapter.other-statements.example">
            <title>Running a Non-Prepared Statement in a PDO Adapter</title>

            <programlisting language="php"><![CDATA[
$result = $db->getConnection()->exec('DROP TABLE bugs');
]]></programlisting>
        </example>

        <para>
            Similarly, you can access other methods or properties that are
            specific to <acronym>PHP</acronym> database extensions. Be aware, though, that by
            doing this you might constrain your application to the interface
            provided by the extension for a specific brand of <acronym>RDBMS</acronym>.
        </para>

        <para>
            In future versions of <classname>Zend_Db</classname>, there will be opportunities to
            add method entry points for functionality that is common to
            the supported <acronym>PHP</acronym> database extensions. This will not affect
            backward compatibility.
        </para>
    </sect2>

    <sect2 id="zend.db.adapter.server-version">
        <title>Retrieving Server Version</title>

        <para>
            Since release 1.7.2, you could retrieve the server version in <acronym>PHP</acronym>
            syntax style to be able to use <methodname>version_compare()</methodname>. If the
            information isn't available, you will receive <constant>NULL</constant>.
        </para>

        <example id="zend.db.adapter.server-version.example">
            <title>Verifying server version before running a query</title>

            <programlisting language="php"><![CDATA[
$version = $db->getServerVersion();
if (!is_null($version)) {
    if (version_compare($version, '5.0.0', '>=')) {
        // do something
    } else {
        // do something else
    }
} else {
    // impossible to read server version
}
]]></programlisting>
        </example>
    </sect2>

    <sect2 id="zend.db.adapter.adapter-notes">
        <title>Notes on Specific Adapters</title>

        <para>
            This section lists differences between the Adapter classes of which
            you should be aware.
        </para>

        <sect3 id="zend.db.adapter.adapter-notes.ibm-db2">
            <title>IBM DB2</title>

            <itemizedlist>
                <listitem>
                    <para>
                        Specify this Adapter to the <methodname>factory()</methodname> method with
                        the name 'Db2'.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        This Adapter uses the <acronym>PHP</acronym> extension
                        <constant>IBM_DB2</constant>.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <acronym>IBM</acronym> <acronym>DB2</acronym> supports both sequences and
                        auto-incrementing keys. Therefore the arguments to
                        <methodname>lastInsertId()</methodname> are optional. If you give
                        no arguments, the Adapter returns the last value
                        generated for an auto-increment key. If you give
                        arguments, the Adapter returns the last value generated
                        by the sequence named according to the convention
                        '<emphasis>table</emphasis>_<emphasis>column</emphasis>_seq'.
                    </para>
                </listitem>
            </itemizedlist>
        </sect3>

        <sect3 id="zend.db.adapter.adapter-notes.mysqli">
            <title>MySQLi</title>

            <itemizedlist>
                <listitem>
                    <para>
                        Specify this Adapter to the <methodname>factory()</methodname>
                        method with the name 'Mysqli'.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        This Adapter utilizes the <acronym>PHP</acronym> extension mysqli.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        MySQL and MariaDB do not support sequences, so
                        <methodname>lastInsertId()</methodname> ignores its arguments and
                        always returns the last value generated for an
                        auto-increment key. The <methodname>lastSequenceId()</methodname>
                        method returns <constant>NULL</constant>.
                    </para>
                </listitem>
            </itemizedlist>
        </sect3>

        <sect3 id="zend.db.adapter.adapter-notes.oracle">
            <title>Oracle</title>

            <itemizedlist>
                <listitem>
                    <para>
                        Specify this Adapter to the <methodname>factory()</methodname>
                        method with the name 'Oracle'.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        This Adapter uses the <acronym>PHP</acronym> extension oci8.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        Oracle does not support auto-incrementing keys, so you
                        should specify the name of a sequence to
                        <methodname>lastInsertId()</methodname> or
                        <methodname>lastSequenceId()</methodname>.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        The Oracle extension does not support positional
                        parameters. You must use named parameters.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        Currently the <constant>Zend_Db::CASE_FOLDING</constant> option
                        is not supported by the Oracle adapter. To use this
                        option with Oracle, you must use the <acronym>PDO</acronym>
                        <acronym>OCI</acronym> adapter.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        By default, <acronym>LOB</acronym> fields are returned as
                        <acronym>OCI</acronym>-Lob objects. You could retrieve them as string for
                        all requests by using driver options '<property>lob_as_string</property>' or
                        for particular request by using
                        <methodname>setLobAsString(boolean)</methodname> on adapter or on statement.
                    </para>
                </listitem>
            </itemizedlist>
        </sect3>

        <sect3 id="zend.db.adapter.adapter-notes.sqlsrv">
            <title>Microsoft SQL Server</title>

            <itemizedlist>
                <listitem>
                    <para>
                        Specify this Adapter to the <methodname>factory()</methodname> method with
                        the name 'Sqlsrv'.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        This Adapter uses the <acronym>PHP</acronym> extension sqlsrv
                    </para>
                </listitem>

                <listitem>
                    <para>
                        Only Microsoft <acronym>SQL</acronym> Server 2005 or greater is supported.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        Microsoft <acronym>SQL</acronym> Server does not support sequences, so
                        <methodname>lastInsertId()</methodname> ignores primary key argument and
                        returns the last value generated for an auto-increment key if a table name
                        is specified or a last insert query returned id. The
                        <methodname>lastSequenceId()</methodname> method returns
                        <constant>NULL</constant>.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <classname>Zend_Db_Adapter_Sqlsrv</classname> sets
                        <constant>QUOTED_IDENTIFIER</constant> ON immediately
                        after connecting to a <acronym>SQL</acronym> Server database. This makes the
                        driver use the standard <acronym>SQL</acronym> identifier delimiter symbol
                        (<emphasis>"</emphasis>) instead of the proprietary square-brackets
                        syntax <acronym>SQL</acronym> Server uses for delimiting identifiers.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        You can specify <property>driver_options</property> as a key in the options
                        array. The value can be a anything from here <ulink
                            url="http://msdn.microsoft.com/en-us/library/cc296161(SQL.90).aspx">http://msdn.microsoft.com/en-us/library/cc296161(SQL.90).aspx</ulink>.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        You can use <methodname>setTransactionIsolationLevel()</methodname> to set
                        isolation level for current connection. The value can be
                        <constant>SQLSRV_TXN_READ_UNCOMMITTED</constant>,
                        <constant>SQLSRV_TXN_READ_COMMITTED</constant>,
                        <constant>SQLSRV_TXN_REPEATABLE_READ</constant>,
                        <constant>SQLSRV_TXN_SNAPSHOT</constant> or
                        <constant>SQLSRV_TXN_SERIALIZABLE</constant>.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        As of Zend Framework 1.9, the minimal supported build of the
                        <acronym>PHP</acronym> <acronym>SQL</acronym> Server extension from
                        Microsoft is 1.0.1924.0. and the <acronym>MSSQL</acronym> Server Native
                        Client version 9.00.3042.00.
                    </para>
                </listitem>
            </itemizedlist>
        </sect3>

        <sect3 id="zend.db.adapter.adapter-notes.pdo-ibm">
            <title>PDO for IBM DB2 and Informix Dynamic Server (IDS)</title>

            <itemizedlist>
                <listitem>
                    <para>
                        Specify this Adapter to the <methodname>factory()</methodname>
                        method with the name '<classname>Pdo_Ibm</classname>'.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        This Adapter uses the <acronym>PHP</acronym> extensions
                        <acronym>PDO</acronym> and <constant>PDO_IBM</constant>.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        You must use at least <constant>PDO_IBM</constant> extension version 1.2.2.
                        If you have an earlier version of this extension, you
                        must upgrade the <constant>PDO_IBM</constant> extension from
                        <acronym>PECL</acronym>.
                    </para>
                </listitem>
            </itemizedlist>
        </sect3>

        <sect3 id="zend.db.adapter.adapter-notes.pdo-mssql">
            <title>PDO Microsoft SQL Server</title>

            <itemizedlist>
                <listitem>
                    <para>
                        Specify this Adapter to the <methodname>factory()</methodname>
                        method with the name '<classname>Pdo_Mssql</classname>'.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        This Adapter uses the <acronym>PHP</acronym> extensions pdo and pdo_dblib.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        Microsoft <acronym>SQL</acronym> Server does not support sequences, so
                        <methodname>lastInsertId()</methodname> ignores its arguments and
                        always returns the last value generated for an
                        auto-increment key. The <methodname>lastSequenceId()</methodname>
                        method returns <constant>NULL</constant>.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        If you are working with unicode strings in an encoding other than
                        <acronym>UCS</acronym>-2 (such as <acronym>UTF</acronym>-8), you may have to
                        perform a conversion in your application code or store the data in a binary
                        column. Please refer to <ulink
                            url="http://support.microsoft.com/kb/232580">Microsoft's Knowledge
                            Base</ulink> for more information.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        <classname>Zend_Db_Adapter_Pdo_Mssql</classname> sets
                        <constant>QUOTED_IDENTIFIER</constant> ON immediately
                        after connecting to a <acronym>SQL</acronym> Server database. This makes the
                        driver use the standard <acronym>SQL</acronym> identifier delimiter symbol
                        (") instead of the proprietary square-brackets syntax <acronym>SQL</acronym>
                        Server uses for delimiting identifiers.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        You can specify <property>pdoType</property> as a key in the
                        options array. The value can be "mssql" (the default),
                        "dblib", "freetds", or "sybase". This option affects
                        the <acronym>DSN</acronym> prefix the adapter uses when constructing the
                        <acronym>DSN</acronym> string. Both "freetds" and "sybase" imply a prefix
                        of "sybase:", which is used for the
                        <ulink url="http://www.freetds.org/">FreeTDS</ulink> set
                        of libraries.
                        See also
                        <ulink url="http://www.php.net/manual/en/ref.pdo-dblib.connection.php">
                        http://www.php.net/manual/en/ref.pdo-dblib.connection.php</ulink>
                        for more information on the <acronym>DSN</acronym> prefixes used in this
                        driver.
                    </para>
                </listitem>
            </itemizedlist>
        </sect3>

        <sect3 id="zend.db.adapter.adapter-notes.pdo-mysql">
            <title>PDO MySQL</title>

            <itemizedlist>
                <listitem>
                    <para>
                        Specify this Adapter to the <methodname>factory()</methodname>
                        method with the name '<classname>Pdo_Mysql</classname>'.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        This Adapter uses the <acronym>PHP</acronym> extensions pdo and pdo_mysql.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        MySQL and MariaDB do not support sequences, so
                        <methodname>lastInsertId()</methodname> ignores its arguments and
                        always returns the last value generated for an
                        auto-increment key. The <methodname>lastSequenceId()</methodname>
                        method returns <constant>NULL</constant>.
                    </para>
                </listitem>
            </itemizedlist>
        </sect3>

        <sect3 id="zend.db.adapter.adapter-notes.pdo-oci">
            <title>PDO Oracle</title>

            <itemizedlist>
                <listitem>
                    <para>
                        Specify this Adapter to the <methodname>factory()</methodname>
                        method with the name '<classname>Pdo_Oci</classname>'.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        This Adapter uses the <acronym>PHP</acronym> extensions pdo and pdo_oci.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        Oracle does not support auto-incrementing keys, so you
                        should specify the name of a sequence to
                        <methodname>lastInsertId()</methodname> or
                        <methodname>lastSequenceId()</methodname>.
                    </para>
                </listitem>
            </itemizedlist>
        </sect3>

        <sect3 id="zend.db.adapter.adapter-notes.pdo-pgsql">
            <title>PDO PostgreSQL</title>

            <itemizedlist>
                <listitem>
                    <para>
                        Specify this Adapter to the <methodname>factory()</methodname>
                        method with the name '<classname>Pdo_Pgsql</classname>'.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        This Adapter uses the <acronym>PHP</acronym> extensions pdo and pdo_pgsql.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        PostgreSQL supports both sequences and auto-incrementing
                        keys. Therefore the arguments to
                        <methodname>lastInsertId()</methodname> are optional. If you give
                        no arguments, the Adapter returns the last value
                        generated for an auto-increment key. If you give
                        arguments, the Adapter returns the last value generated
                        by the sequence named according to the convention
                        '<emphasis>table</emphasis>_<emphasis>column</emphasis>_seq'.
                    </para>
                </listitem>
            </itemizedlist>
        </sect3>

        <sect3 id="zend.db.adapter.adapter-notes.pdo-sqlite">
            <title>PDO SQLite</title>

            <itemizedlist>
                <listitem>
                    <para>
                        Specify this Adapter to the <methodname>factory()</methodname>
                        method with the name '<classname>Pdo_Sqlite</classname>'.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        This Adapter uses the <acronym>PHP</acronym> extensions pdo and pdo_sqlite.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        SQLite does not support sequences, so
                        <methodname>lastInsertId()</methodname> ignores its arguments and
                        always returns the last value generated for an
                        auto-increment key. The <methodname>lastSequenceId()</methodname>
                        method returns <constant>NULL</constant>.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        To connect to an SQLite2 database, specify
                        <command>'sqlite2' => true</command> in the array of
                        parameters when creating an instance of the
                        <classname>Pdo_Sqlite</classname> Adapter.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        To connect to an in-memory SQLite database,
                        specify <command>'dbname' => ':memory:'</command> in the
                        array of parameters when creating an instance of
                        the <classname>Pdo_Sqlite</classname> Adapter.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        Older versions of the SQLite driver for <acronym>PHP</acronym> do not seem
                        to support the <acronym>PRAGMA</acronym> commands necessary to ensure that
                        short column names are used in result sets. If you
                        have problems that your result sets are returned with
                        keys of the form "tablename.columnname" when you do a
                        join query, then you should upgrade to the current
                        version of <acronym>PHP</acronym>.
                    </para>
                </listitem>
            </itemizedlist>
        </sect3>

        <sect3 id="zend.db.adapter.adapter-notes.firebird">
            <title>Firebird (Interbase)</title>

            <itemizedlist>
                <listitem>
                    <para>
                        This Adapter uses the <acronym>PHP</acronym> extension php_interbase.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        Firebird (Interbase) does not support auto-incrementing
                        keys, so you should specify the name of a sequence to
                        <methodname>lastInsertId()</methodname> or
                        <methodname>lastSequenceId()</methodname>.
                    </para>
                </listitem>

                <listitem>
                    <para>
                        Currently the <constant>Zend_Db::CASE_FOLDING</constant> option
                        is not supported by the Firebird (Interbase) adapter.
                        Unquoted identifiers are automatically returned in
                        upper case.
                    </para>
                </listitem>

                <listitem>
                    <para>Adapter name is <classname>ZendX_Db_Adapter_Firebird</classname>.</para>

                    <para>
                        Remember to use the param adapterNamespace with value
                        <classname>ZendX_Db_Adapter</classname>.
                    </para>

                    <para>
                        We recommend to update the <filename>gds32.dll</filename> (or linux
                        equivalent) bundled with <acronym>PHP</acronym>, to the same version of the
                        server. For Firebird the equivalent <filename>gds32.dll</filename> is
                        <filename>fbclient.dll</filename>.
                    </para>

                    <para>
                        By default all identifiers (tables names, fields) are returned in upper
                        case.
                    </para>
                </listitem>
            </itemizedlist>
        </sect3>
    </sect2>
</sect1>
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