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|
<html>
<head>
<title>firstworks Programming with SQL Relay using the Python DB API</title>
<link href="../css/styles.css" rel="stylesheet">
</head>
<body>
<span class="heading1">Programming with SQL Relay using the Python DB API</span><br><br>
<ul>
<li><a href="#session">Establishing a Sessions</a></li>
<li><a href="#query">Executing Queries</a></li>
<li><a href="#commit">Commits and Rollbacks</a></li>
<li><a href="#temptables">Temporary Tables</a></li>
<li><a href="#errors">Catching Errors</a></li>
<li><a href="#bindvars">Bind Variables</a></li>
<li><a href="#rebinding">Re-Binding and Re-Executing</a></li>
<li><a href="#fields">Accessing Fields in the Result Set</a></li>
<li><a href="#cursors">Cursors</a></li>
<li><a href="#columns">Getting Column Information</a></li>
<li><a href="#storedprocedures">Stored Procedures</a></li>
</ul>
<a name="session"></a>
<span class="heading2">Establishing a Session</span><br><br>
<p>To use SQL Relay, you have to identify the connection that you intend to
use.</p>
<blockquote>
<PRE>
<FONT color=#a020f0>from</FONT> SQLRelay <FONT color=#a020f0>import</FONT> PySQLRDB
con=PySQLRDB.connect('<FONT color=#ff00ff>host</FONT>',9000,'','<FONT color=#ff00ff>user</FONT>','<FONT color=#ff00ff>password</FONT>',0,1)
cur=con.cursor()
... execute some queries ...
</PRE>
</blockquote>
<p>After calling the connect(), a session is established when the first
execute() is run.</p>
<p>For the duration of the session, the client stays connected to a database
connection daemon. While one client is connected, no other client can connect.
Care should be taken to minimize the length of a session.</p>
<p>If you're using a transactional database, ending a session has a catch.
Database connection daemons can be configured to send either a commit or
rollback at the end of a session if DML queries were executed during the
session with no commit or rollback. Program accordingly.</p>
<a name="query"></a>
<span class="heading2">Executing Queries</span><br><br>
<p>Call execute() to run a query.</p>
<blockquote>
<PRE>
<FONT color=#a020f0>from</FONT> SQLRelay <FONT color=#a020f0>import</FONT> PySQLRDB
con=PySQLRDB.connect('<FONT color=#ff00ff>host</FONT>',9000,'','<FONT color=#ff00ff>user</FONT>','<FONT color=#ff00ff>password</FONT>',0,1)
cur=con.cursor()
cur.execute('<FONT color=#ff00ff>select * from my_table</FONT>')
... process the result set ...
</PRE>
</blockquote>
<a name="commit"></a>
<span class="heading2">Commits and Rollbacks</span><br><br>
<p>If you need to execute a commit or rollback, you should use the commit()
and rollback() methods rather than sending a "commit" or "rollback" query.
There are two reasons for this. First, it's much more efficient to call the
methods. Second, if you're writing code that can run on transactional or
non-transactional databases, some non-transactional databases will throw errors
if they receive a "commit" or "rollback" query, but by calling the commit()
and rollback() methods you instruct the database connection daemon to call the
commit and rollback API methods for that database rather than issuing them as
queries. If the API's have no commit or rollback methods, the calls do nothing
and the database throws no error. This is especially important when using SQL
Relay with ODBC.</p>
<a name="temptables"></a>
<span class="heading2">Temporary Tables</span><br><br>
<p>Some databases support temporary tables. That is, tables which are
automatically dropped or truncated when an application closes it's connection
to the database or when a transaction is committed or rolled back.</p>
<p>For databases which drop or truncate tables when a transaction is committed
or rolled back, temporary tables work naturally.</p>
<p>However, for databases which drop or truncate tables when an application
closes it's connection to the database, there is an issue. Since SQL Relay
maintains persistent database connections, when an application disconnects from
SQL Relay, the connection between SQL Relay and the database remains, so
the database does not know to drop or truncate the table. To remedy this
situation, SQL Relay parses each query to see if it created a temporary table,
keeps a list of temporary tables and drops (or truncates them) when the
application disconnects from SQL Relay. Since each database has slightly
different syntax for creating a temporary table, SQL Relay parses each query
according to the rules for that database.</p>
<p>In effect, temporary tables should work when an application connects to
SQL Relay in the same manner that they would work if the application connected
directly to the database.</p>
<a name="errors"></a>
<span class="heading2">Catching Errors</span><br><br>
<p>If your call to execute() raises an exception, the query failed.
You can find out why by catching the exception.</p>
<blockquote>
<PRE>
<FONT color=#a020f0>from</FONT> SQLRelay <FONT color=#a020f0>import</FONT> PySQLRDB
con=PySQLRDB.connect('<FONT color=#ff00ff>host</FONT>',9000,'','<FONT color=#ff00ff>user</FONT>','<FONT color=#ff00ff>password</FONT>',0,1)
cur=con.cursor()
<B><FONT color=#a52a2a>try</FONT></B>:
cur.execute('<FONT color=#ff00ff>select * from my_nonexistant_table</FONT>')
<B><FONT color=#a52a2a>except</FONT></B> PySQLRDB.DatabaseError, e:
print e
</PRE>
</blockquote>
<a name="bindvars"></a>
<span class="heading2">Bind Variables</span><br><br>
<p>Programs rarely execute fixed queries. More often than not, some part
of the query is dynamically generated. The Python DB API provides a means
for using bind variables in those queries.</p>
<p>For a detailed discussion of binds, see
<a href="binds.html">this document</a>.</p>
<blockquote>
<PRE>
<FONT color=#a020f0>from</FONT> SQLRelay <FONT color=#a020f0>import</FONT> PySQLRDB
con=PySQLRDB.connect('<FONT color=#ff00ff>host</FONT>',9000,'','<FONT color=#ff00ff>user</FONT>','<FONT color=#ff00ff>password</FONT>',0,1)
cur=con.cursor()
cur.execute('<FONT color=#ff00ff>select * from my_table where column1>:val1 and column2=:val2 and column3<:val3</FONT>',{'<FONT color=#ff00ff>val1</FONT>':1,'<FONT color=#ff00ff>val2</FONT>':'<FONT color=#ff00ff>hello</FONT>','<FONT color=#ff00ff>val3</FONT>':50.546})
... process the result set ...
</PRE>
</blockquote>
<p>When passing a floating point number in as a bind or substitution variable,
you have to supply precision and scale for the number. See
<a href="precisionscale.html">this page</a> for a discussion of precision and
scale.</p>
<a name="rebinding"></a>
<span class="heading2">Re-Binding and Re-Execution</span><br><br>
<p>A feature of the prepare/bind/execute paradigm is the ability to prepare,
bind and execute a query once, then re-bind and re-execute the query
over and over without re-preparing it. If your backend database natively
supports this paradigm, you can reap a substantial performance improvement.</p>
<p>The Python DB API supports this paradigm via the executemany method. If you
pass in a list of parameter dictionaries, the query will be re-executed for
each dictionary of bind variable/values.</p>
<blockquote>
<PRE>
<FONT color=#a020f0>from</FONT> SQLRelay <FONT color=#a020f0>import</FONT> PySQLRDB
con=PySQLRDB.connect('<FONT color=#f800f8>host</FONT>',9000,'','<FONT color=#f800f8>user</FONT>','<FONT color=#f800f8>password</FONT>',0,1)
cur=con.cursor()
cur.executemany('<FONT color=#ff00ff>insert into my_table values (:val1,:val2,:val3)</FONT>',
[{'<FONT color=#ff00ff>val1</FONT>':1,'<FONT color=#ff00ff>val2</FONT>':'<FONT color=#ff00ff>hello</FONT>','<FONT color=#ff00ff>val3</FONT>':1.11},
{'<FONT color=#ff00ff>val1</FONT>':2,'<FONT color=#ff00ff>val2</FONT>':'<FONT color=#ff00ff>hi</FONT>','<FONT color=#ff00ff>val3</FONT>':2.22},
{'<FONT color=#ff00ff>val1</FONT>':3,'<FONT color=#ff00ff>val2</FONT>':'<FONT color=#ff00ff>bye</FONT>','<FONT color=#ff00ff>val3</FONT>':3,33}])
</PRE>
</blockquote>
<a name="fields"></a>
<span class="heading2">Accessing Fields in the Result Set</span><br><br>
<p>The fetchone(), fetchmany() and fetchall() methods are useful for processing
result sets. fetchone() returns a list of values. fetchmany() and fetchall()
each return a list of rows where each row is a list of values.</p>
<p>The rowcount member variable gives the number of rows in the result set of
a select query or the number of rows affected by an insert/update/delete query.
</p>
<blockquote>
<PRE>
<FONT color=#a020f0>from</FONT> SQLRelay <FONT color=#a020f0>import</FONT> PySQLRDB
con=PySQLRDB.connect('<FONT color=#ff00ff>host</FONT>',9000,'','<FONT color=#ff00ff>user</FONT>','<FONT color=#ff00ff>password</FONT>',0,1)
cur=con.cursor()
cur.execute('<FONT color=#ff00ff>select * from my_table</FONT>')
print '<FONT color=#ff00ff>rowcount:</FONT>', cur.rowcount
print '<FONT color=#ff00ff>the first row:</FONT>'
print cur.fetchone()
print
print '<FONT color=#ff00ff>the next three rows:</FONT>'
print cur.fetchmany(3)
print
print '<FONT color=#ff00ff>the rest of the rows:</FONT>'
print cur.fetchall()
print
</PRE>
</blockquote>
<a name="cursors"></a>
<span class="heading2">Cursors</span><br><br>
<p>Cursors make it possible to execute queries while processing the result
set of another query. You can select rows from a table in one query, then
iterate through it's result set, inserting rows into another table, using only
1 database connection for both operations.</p>
<p>For example:</p>
<blockquote>
<PRE>
<FONT color=#a020f0>from</FONT> SQLRelay <FONT color=#a020f0>import</FONT> PySQLRDB
con=PySQLRDB.sqlrconnection('<FONT color=#f800f8>host</FONT>',9000,'','<FONT color=#f800f8>user</FONT>','<FONT color=#f800f8>password</FONT>',0,1)
cursor1=con.cursor()
cursor2=con.cursor()
cursor1.execute('<FONT color=#f800f8>select * from my_huge_table</FONT>')
<B><FONT color=#a02828>for</FONT></B> a in cursor1.fetchall():
cursor2.execute('<FONT color=#f800f8>insert into my_other_table values (:1,:2,:3)</FONT>',{':1',a[0],':2',a[1],':3',a[2]})
</PRE>
</blockquote>
<a name="columns"></a>
<span class="heading2">Getting Column Information</span><br><br>
<p>After executing a query, column information is stored in the desc
variable. desc is a list of tuples. Each tuple corresponds to a column,
containing it's name, type and length. </p>
<blockquote>
<PRE>
<FONT color=#a020f0>from</FONT> SQLRelay <FONT color=#a020f0>import</FONT> PySQLRDB
con=PySQLRDB.connect('<FONT color=#ff00ff>host</FONT>',9000,'','<FONT color=#ff00ff>user</FONT>','<FONT color=#ff00ff>password</FONT>',0,1)
cur=con.cursor()
cur.execute('<FONT color=#ff00ff>select * from my_table</FONT>')
<B><FONT color=#a52a2a>for</FONT></B> name,type,length <B><FONT color=#a52a2a>in</FONT></B> cur.desc:
print '<FONT color=#ff00ff>Name: </FONT>', name
print '<FONT color=#ff00ff>Type: </FONT>', type
print '<FONT color=#ff00ff>Length: </FONT>', length
</PRE>
</blockquote>
<a name="storedprocedures"></a>
<span class="heading2">Stored Procedures</span><br><br>
<p>Many databases support stored procedures. Stored procedures are sets of
queries and procedural code that are executed inside of the database itself.
For example, a stored procedure may select rows from one table, iterate through
the result set and, based on the values in each row, insert, update or delete
rows in other tables. A client program could do this as well, but a stored
procedure is generally more efficient because queries and result sets don't
have to be sent back and forth between the client and database. Also, stored
procedures are generally stored in the database in a compiled state, while
queries may have to be re-parsed and re-compiled each time they are sent.</p>
<p>While many databases support stored procedures. The syntax for creating
and executing stored procedures varies greatly between databases.</p>
<p>SQL Relay supports stored procedures for most databases, but there are
some caveats. Stored procedures are not currently supported when using FreeTDS
against Sybase or Microsoft SQL Server. Blob/Clob bind variables are only
supported in Oracle 8i or higher. Sybase stored procedures must use varchar
output parameters.</p>
<p>Stored procedures typically take input paramters from client programs through
input bind variables and return values back to client programs either through
bind variables or result sets. Stored procedures can be broken down into
several categories, based on the values that they return. Some stored
procedures don't return any values, some return a single value, some return
multiple values and some return entire result sets.</p>
<span class="heading3">No Values</span><br>
<p>Some stored procedures don't return any values. Below are examples,
illustrating how to create, execute and drop this kind of stored procedure for
each database that SQL Relay supports.</p>
<span class="heading4">Oracle</span><br>
<p>To create the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>create</b></font> <font color="#6b59ce">procedure</font> testproc(in1 <font color="#a52829"><b>in</b></font> <font color="#298a52"><b>number</b></font>, in2 <font color="#a52829"><b>in</b></font> <font color="#298a52"><b>number</b></font>, in3 <font color="#a52829"><b>in</b></font> <font color="#298a52"><b>varchar2</b></font>) <font color="#6b59ce">is</font>
<font color="#6b59ce">begin</font>
<font color="#a52829"><b>insert</b></font> <font color="#6b59ce">into</font> mytable <font color="#6b59ce">values</font> (in1,in2,in3);
<font color="#6b59ce">end</font>;
</pre>
</blockquote>
<p>To execute the stored procedure from an SQL Relay program, use code like the
following.</p>
<blockquote>
<pre>
cur.execute('<font color="#ff00ff">begin testproc(:in1,:in2,:in3); end;</font>',{'<font color="#ff00ff">in1</font>':1,'<font color="#ff00ff">in2</font>':1.1,'<font color="#ff00ff">in3</font>':'<font color="#ff00ff">hello</font>'})
</pre>
</blockquote>
<p>To drop the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>drop</b></font> <font color="#6b59ce">procedure</font> testproc
</pre>
</blockquote>
<span class="heading4">Sybase and Microsoft SQL Server</span><br>
<p>To create the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>create</b></font> <font color="#6b59ce">procedure</font> testproc @in1 int, @in2 <font color="#298a52"><b>float</b></font>, @in3 <font color="#298a52"><b>varchar</b></font>(<font color="#ff00ff">20</font>) <font color="#6b59ce">as</font>
<font color="#a52829"><b>insert</b></font> <font color="#6b59ce">into</font> mytable <font color="#6b59ce">values</font> (@in1,@in2,@in3)
</pre>
</blockquote>
<p>To execute the stored procedure from an SQL Relay program, use code like the
following.</p>
<blockquote>
<pre>
cur.execute('<font color="#ff00ff">exec testproc</font>',{'<font color="#ff00ff">in1</font>':1,'<font color="#ff00ff">in2</font>':1.1,'<font color="#ff00ff">in3</font>':'<font color="#ff00ff">hello</font>'})
</pre>
</blockquote>
<p>To drop the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>drop</b></font> <font color="#6b59ce">procedure</font> testproc
</pre>
</blockquote>
<span class="heading4">Interbase and Firebird</span><br>
<p>To create the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>create</b></font> <font color="#6b59ce">procedure</font> testproc(in1 <font color="#298a52"><b>integer</b></font>, in2 <font color="#298a52"><b>float</b></font>, in3 <font color="#298a52"><b>varchar</b></font>(<font color="#ff00ff">20</font>)) <font color="#6b59ce">as</font>
<font color="#6b59ce">begin</font>
<font color="#a52829"><b>insert</b></font> <font color="#6b59ce">into</font> mytable <font color="#6b59ce">values</font> (in1,in2,in3);
suspend;
<font color="#6b59ce">end</font>;
</pre>
</blockquote>
<p>To execute the stored procedure from an SQL Relay program, use code like the
following.</p>
<blockquote>
<pre>
cur.execute('<font color="#ff00ff">exec procedure testproc ?, ?, ?</font>',{'<font color="#ff00ff">in1</font>':1,'<font color="#ff00ff">in2</font>':1.1,'<font color="#ff00ff">in3</font>':'<font color="#ff00ff">hello</font>'})
</pre>
</blockquote>
<p>To drop the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>drop</b></font> <font color="#6b59ce">procedure</font> testproc
</pre>
</blockquote>
<span class="heading4">DB2</span><br>
<p>To create the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>create</b></font> <font color="#6b59ce">procedure</font> testproc(<font color="#a52829"><b>in</b></font> in1 int, <font color="#a52829"><b>in</b></font> in2 double, <font color="#a52829"><b>in</b></font> in3 <font color="#298a52"><b>varchar</b></font>(<font color="#ff00ff">20</font>)) language sql
<font color="#6b59ce">begin</font>
<font color="#a52829"><b>insert</b></font> <font color="#6b59ce">into</font> mytable <font color="#6b59ce">values</font> (in1,in2,in3);
<font color="#6b59ce">end</font>;
</pre>
</blockquote>
<p>To execute the stored procedure from an SQL Relay program, use code like the
following.</p>
<blockquote>
<pre>
cur.execute('<font color="#ff00ff">call testproc(?,?,?)</font>',{'<font color="#ff00ff">in1</font>':1,'<font color="#ff00ff">in2</font>':1.1,'<font color="#ff00ff">in3</font>':'<font color="#ff00ff">hello</font>'})
</pre>
</blockquote>
<p>To drop the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>drop</b></font> <font color="#6b59ce">procedure</font> testproc
</pre>
</blockquote>
<span class="heading4">Postgresql</span><br>
<p>To create the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>create</b></font> <font color="#6b59ce">function</font> testproc(int,<font color="#298a52"><b>float</b></font>,<font color="#298a52"><b>varchar</b></font>(<font color="#ff00ff">20</font>)) returns void <font color="#6b59ce">as</font> '
<font color="#6b59ce">begin</font>
<font color="#a52829"><b>insert</b></font> <font color="#6b59ce">into</font> mytable <font color="#6b59ce">values</font> ($<font color="#ff00ff">1</font>,$<font color="#ff00ff">2</font>,$<font color="#ff00ff">3</font>);
<font color="#6b59ce">return</font>;
<font color="#6b59ce">end</font>;' language plpgsql
</pre>
</blockquote>
<p>To execute the stored procedure from an SQL Relay program, use code like the
following.</p>
<blockquote>
<pre>
cur.execute('<font color="#ff00ff">select testproc(:in1,:in2,:in3)</font>',{'<font color="#ff00ff">in1</font>':1,'<font color="#ff00ff">in2</font>':1.1,'<font color="#ff00ff">in3</font>':'<font color="#ff00ff">hello</font>'})
</pre>
</blockquote>
<p>To drop the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>drop</b></font> <font color="#6b59ce">procedure</font> testproc
</pre>
</blockquote>
<br><span class="heading3">Single Values</span><br>
<p>Some stored procedures return single values. Below are examples,
illustrating how to create, execute and drop this kind of stored procedure for
each database that SQL Relay supports.</p>
<span class="heading4">Oracle</span><br>
<p>To create the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>create</b></font> <font color="#6b59ce">function</font> testproc(in1 <font color="#a52829"><b>in</b></font> <font color="#298a52"><b>number</b></font>, in2 <font color="#a52829"><b>in</b></font> <font color="#298a52"><b>number</b></font>, in3 <font color="#a52829"><b>in</b></font> <font color="#298a52"><b>varchar2</b></font>) returns <font color="#298a52"><b>number</b></font> <font color="#6b59ce">is</font>
<font color="#6b59ce">begin</font>
<font color="#6b59ce">return</font> in1;
<font color="#6b59ce">end</font>;
</pre>
</blockquote>
<p>To execute the stored procedure from an SQL Relay program, use code like the
following.</p>
<blockquote>
<pre>
cur.execute('<font color="#ff00ff">select testproc(:in1,:in2,:in3) from dual</font>',{'<font color="#ff00ff">in1</font>':1,'<font color="#ff00ff">in2</font>':1.1,'<font color="#ff00ff">in3</font>':'<font color="#ff00ff">hello</font>'})
result=cur.fetchone()[0]
</pre>
</blockquote>
<p>To drop the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>drop</b></font> <font color="#6b59ce">function</font> testproc
</pre>
</blockquote>
<span class="heading4">Sybase and Microsoft SQL Server</span><br>
<p>In Sybase and Microsoft SQL Server, stored procedures return values
through output parameters rather than as return values of the procedure
itself. However, the SQL Relay Python DBdriver does not currently support
output parameters.</p>
<span class="heading4">Interbase and Firebird</span><br>
<p>To create the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>create</b></font> <font color="#6b59ce">procedure</font> testproc(in1 <font color="#298a52"><b>integer</b></font>, in2 <font color="#298a52"><b>float</b></font>, in3 <font color="#298a52"><b>varchar</b></font>(<font color="#ff00ff">20</font>)) returns (out1 <font color="#298a52"><b>integer</b></font>) <font color="#6b59ce">as</font>
<font color="#6b59ce">begin</font>
out1=in1;
suspend;
<font color="#6b59ce">end</font>;
</pre>
</blockquote>
<p>To execute the stored procedure from an SQL Relay program, use code like the
following.</p>
<blockquote>
<pre>
cur.execute('<font color="#ff00ff">select * from testproc(?,?,?)</font>',{'<font color="#ff00ff">in1</font>':1,'<font color="#ff00ff">in2</font>':1.1,'<font color="#ff00ff">in3</font>':'<font color="#ff00ff">hello</font>'})
result=cur.fetchone()[0]
</pre>
</blockquote>
<p>To drop the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>drop</b></font> <font color="#6b59ce">procedure</font> testproc
</pre>
</blockquote>
<span class="heading4">DB2</span><br>
<p>In DB2, stored procedures return values through output parameters rather
than as return values of the procedure itself. However, the SQL Relay Python
DB driver does not currently support output parameters.</p>
<span class="heading4">Postgresql</span><br>
<p>To create the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>create</b></font> <font color="#6b59ce">function</font> testfunc(int,<font color="#298a52"><b>float</b></font>,<font color="#298a52"><b>char</b></font>(<font color="#ff00ff">20</font>)) returns int <font color="#6b59ce">as</font> '
declare
in1 int;
in2 <font color="#298a52"><b>float</b></font>;
in3 <font color="#298a52"><b>char</b></font>(<font color="#ff00ff">20</font>);
<font color="#6b59ce">begin</font>
in1:=$<font color="#ff00ff">1</font>;
<font color="#6b59ce">return</font>;
<font color="#6b59ce">end</font>;
' language plpgsql
</pre>
</blockquote>
<p>To execute the stored procedure from an SQL Relay program, use code like the
following.</p>
<blockquote>
<pre>
cur.execute('<font color="#ff00ff">select * from testfunc(:in1,:in2,:in3)</font>',{'<font color="#ff00ff">in1</font>':1,'<font color="#ff00ff">in2</font>':1.1,'<font color="#ff00ff">in3</font>':'<font color="#ff00ff">hello</font>'})
result=cur.fetchone()[0]
</pre>
</blockquote>
<p>To drop the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>drop</b></font> <font color="#6b59ce">function</font> testfunc(int,<font color="#298a52"><b>float</b></font>,<font color="#298a52"><b>char</b></font>(<font color="#ff00ff">20</font>))
</pre>
</blockquote>
<br><span class="heading3">Multiple Values</span><br>
<p>Some stored procedures return multiple values. Below are examples,
illustrating how to create, execute and drop this kind of stored procedure for
each database that SQL Relay supports.</p>
<span class="heading4">Oracle</span><br>
<p>In Oracle, stored procedures can return values through output parameters or
as return values of the procedure itself. If a procedure needs to return
multiple values, it can return one of them as the return value of the procedure
itself, but the rest must be returned through output parameters. However, the
SQL Relay Python DB driver does not currently support output parameters.</p>
<span class="heading4">Sybase and Microsoft SQL Server</span><br>
<p>In Sybase and Microsoft SQL Server, stored procedures return values
through output parameters rather than as return values of the procedure
itself. However, the SQL Relay Python DB driver does not currently support
output parameters.</p>
<span class="heading4">Interbase and Firebird</span><br>
<p>To create the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>create</b></font> <font color="#6b59ce">procedure</font> testproc(in1 <font color="#298a52"><b>integer</b></font>, in2 <font color="#298a52"><b>float</b></font>, in3 <font color="#298a52"><b>varchar</b></font>(<font color="#ff00ff">20</font>)) returns (out1 <font color="#298a52"><b>integer</b></font>, out2 <font color="#298a52"><b>float</b></font>, out3 <font color="#298a52"><b>varchar</b></font>(<font color="#ff00ff">20</font>)) <font color="#6b59ce">as</font>
<font color="#6b59ce">begin</font>
out1=in1;
out2=in2;
out3=in3;
suspend;
<font color="#6b59ce">end</font>;
</pre>
</blockquote>
<p>To execute the stored procedure from an SQL Relay program, use code like the
following.</p>
<blockquote>
<pre>
cur.execute('<font color="#ff00ff">select * from testfunc(?,?,?)</font>',{'<font color="#ff00ff">in1</font>':1,'<font color="#ff00ff">in2</font>':1.1,'<font color="#ff00ff">in3</font>':'<font color="#ff00ff">hello</font>'})
out1=cur.fetchone()[0]
out2=cur.fetchone()[1]
out3=cur.fetchone()[2]
</pre>
</blockquote>
<p>To drop the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>drop</b></font> <font color="#6b59ce">procedure</font> testproc
</pre>
</blockquote>
<span class="heading4">DB2</span><br>
<p>In DB2, stored procedures return values through output parameters rather
than as return values of the procedure itself. However, the SQL Relay Python
DB driver does not currently support output parameters.</p>
<span class="heading4">Postgresql</span><br>
<p>To create the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>create</b></font> <font color="#6b59ce">function</font> testfunc(int,<font color="#298a52"><b>float</b></font>,<font color="#298a52"><b>char</b></font>(<font color="#ff00ff">20</font>)) returns record <font color="#6b59ce">as</font> '
declare
output record;
<font color="#6b59ce">begin</font>
<font color="#a52829"><b>select</b></font> $<font color="#ff00ff">1</font>,$<font color="#ff00ff">2</font>,$<font color="#ff00ff">3</font> <font color="#6b59ce">into</font> output;
<font color="#6b59ce">return</font> output;
<font color="#6b59ce">end</font>;
' language plpgsql
</pre>
</blockquote>
<p>To execute the stored procedure from an SQL Relay program, use code like the
following.</p>
<blockquote>
<pre>
cur.execute('<font color="#ff00ff">select * from testfunc(:in1,:in2,:in3) as (col1 int, col2 float, col3 char(20))</font>',{'<font color="#ff00ff">in1</font>':1,'<font color="#ff00ff">in2</font>':1.1,'<font color="#ff00ff">in3</font>':'<font color="#ff00ff">hello</font>'})
out1=cur.fetchone()[0]
out2=cur.fetchone()[1]
out3=cur.fetchone()[2]
</pre>
</blockquote>
<p>To drop the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>drop</b></font> <font color="#6b59ce">function</font> testfunc(int,<font color="#298a52"><b>float</b></font>,<font color="#298a52"><b>char</b></font>(<font color="#ff00ff">20</font>))
</pre>
</blockquote>
<br><span class="heading3">Result Sets</span><br>
<p>Some stored procedures return entire result sets. Below are examples,
illustrating how to create, execute and drop this kind of stored procedure for
each database that SQL Relay supports.</p>
<span class="heading4">Oracle</span><br>
<p>Stored procedures in Oracle can return open cursors as return values or
output parameters. A client-side cursor can be bound to this open cursor and
rows can be fetched from it. However, the SQL Relay Python DB driver does not
currently support output parameters.</p>
<span class="heading4">Sybase and Microsoft SQL Server</span><br>
<p>Stored procedures in Sybase and Microsoft SQL Server can return a result
set if the last command in the procedure is a select query, however SQL Relay
doesn't currently support stored procedures that return result sets.</p>
<span class="heading4">Interbase and Firebird</span><br>
<p>Stored procedures in Interbase and Firebird can return a result set if a
select query in the procedure selects values into the output parameters and
then issues a suspend command, however SQL Relay doesn't currently support
stored procedures that return result sets.</p>
<span class="heading4">DB2</span><br>
<p>Stored procedures in DB2 can return a result set if the procedure is declared
to return one, however SQL Relay doesn't currently support stored procedures
that return result sets.</p>
<span class="heading4">Postgresql</span><br>
<p>To create the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>create</b></font> <font color="#6b59ce">function</font> testfunc() returns setof record <font color="#6b59ce">as</font> '
declare output record;
<font color="#6b59ce">begin</font>
<font color="#6b59ce">for</font> output <font color="#a52829"><b>in</b></font> <font color="#a52829"><b>select</b></font> * <font color="#6b59ce">from</font> mytable <font color="#6b59ce">loop</font>
<font color="#6b59ce">return</font> next output;
<font color="#6b59ce">end</font> <font color="#6b59ce">loop</font>;
<font color="#6b59ce">return</font>;
<font color="#6b59ce">end</font>;
' language plpgsql
</pre>
</blockquote>
<p>To execute the stored procedure from an SQL Relay program, use code like the
following.</p>
<blockquote>
<pre>
cur.execute('<font color="#ff00ff">select * from testfunc() as (col1 int, col2 float, col3 char(20))</font>',{'<font color="#ff00ff">in1</font>':1,'<font color="#ff00ff">in2</font>':1.1,'<font color="#ff00ff">in3</font>':'<font color="#ff00ff">hello</font>'})
result=cur.fetchall()
</pre>
</blockquote>
<p>To drop the stored procedure, run a query like the following.</p>
<blockquote>
<pre>
<font color="#a52829"><b>drop</b></font> <font color="#6b59ce">function</font> testfunc
</pre>
</blockquote>
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