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<a href="intro.html"><h2>SQLite C Interface</h2></a><h2>Dynamically Typed Value Object</h2><blockquote><pre>typedef struct Mem sqlite3_value;
</pre></blockquote><p>
SQLite uses the sqlite3_value object to represent all values
that can be stored in a database table. SQLite uses dynamic typing
for the values it stores. Values stored in sqlite3_value objects
can be integers, floating point values, strings, BLOBs, or NULL.</p>
<p>An sqlite3_value object may be either "protected" or "unprotected".
Some interfaces require a protected sqlite3_value. Other interfaces
will accept either a protected or an unprotected sqlite3_value.
Every interface that accepts sqlite3_value arguments specifies
whether or not it requires a protected sqlite3_value.</p>
<p>The terms "protected" and "unprotected" refer to whether or not
a mutex is held. An internal mutex is held for a protected
sqlite3_value object but no mutex is held for an unprotected
sqlite3_value object. If SQLite is compiled to be single-threaded
(with <a href="../compile.html#threadsafe">SQLITE_THREADSAFE=0</a> and with <a href="../c3ref/threadsafe.html">sqlite3_threadsafe()</a> returning 0)
or if SQLite is run in one of reduced mutex modes
<a href="../c3ref/c_config_covering_index_scan.html#sqliteconfigsinglethread">SQLITE_CONFIG_SINGLETHREAD</a> or <a href="../c3ref/c_config_covering_index_scan.html#sqliteconfigmultithread">SQLITE_CONFIG_MULTITHREAD</a>
then there is no distinction between protected and unprotected
sqlite3_value objects and they can be used interchangeably. However,
for maximum code portability it is recommended that applications
still make the distinction between protected and unprotected
sqlite3_value objects even when not strictly required.</p>
<p>The sqlite3_value objects that are passed as parameters into the
implementation of <a href="../c3ref/create_function.html">application-defined SQL functions</a> are protected.
The sqlite3_value object returned by
<a href="../c3ref/column_blob.html">sqlite3_column_value()</a> is unprotected.
Unprotected sqlite3_value objects may only be used with
<a href="../c3ref/result_blob.html">sqlite3_result_value()</a> and <a href="../c3ref/bind_blob.html">sqlite3_bind_value()</a>.
The <a href="../c3ref/value_blob.html">sqlite3_value_type()</a> family of
interfaces require protected sqlite3_value objects.
</p><p>See also lists of
<a href="objlist.html">Objects</a>,
<a href="constlist.html">Constants</a>, and
<a href="funclist.html">Functions</a>.</p>
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