165 lines
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HTML
165 lines
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<!-- keywords: {protected sqlite3_value} sqlite3_value {unprotected sqlite3_value} -->
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<a href="intro.html"><h2>SQLite C Interface</h2></a>
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<h2>Dynamically Typed Value Object</h2>
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</div>
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<blockquote><pre>
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typedef struct sqlite3_value sqlite3_value;
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</pre></blockquote>
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<p>
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SQLite uses the sqlite3_value object to represent all values
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that can be stored in a database table. SQLite uses dynamic typing
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for the values it stores. Values stored in sqlite3_value objects
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can be integers, floating point values, strings, BLOBs, or NULL.</p>
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<p>An sqlite3_value object may be either "protected" or "unprotected".
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Some interfaces require a protected sqlite3_value. Other interfaces
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will accept either a protected or an unprotected sqlite3_value.
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Every interface that accepts sqlite3_value arguments specifies
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whether or not it requires a protected sqlite3_value. The
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<a href="../c3ref/value_dup.html">sqlite3_value_dup()</a> interface can be used to construct a new
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protected sqlite3_value from an unprotected sqlite3_value.</p>
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<p>The terms "protected" and "unprotected" refer to whether or not
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a mutex is held. An internal mutex is held for a protected
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sqlite3_value object but no mutex is held for an unprotected
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sqlite3_value object. If SQLite is compiled to be single-threaded
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(with <a href="../compile.html#threadsafe">SQLITE_THREADSAFE=0</a> and with <a href="../c3ref/threadsafe.html">sqlite3_threadsafe()</a> returning 0)
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or if SQLite is run in one of reduced mutex modes
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<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>
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then there is no distinction between protected and unprotected
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sqlite3_value objects and they can be used interchangeably. However,
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for maximum code portability it is recommended that applications
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still make the distinction between protected and unprotected
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sqlite3_value objects even when not strictly required.</p>
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<p>The sqlite3_value objects that are passed as parameters into the
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implementation of <a href="../appfunc.html">application-defined SQL functions</a> are protected.
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The sqlite3_value object returned by
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<a href="../c3ref/column_blob.html">sqlite3_column_value()</a> is unprotected.
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Unprotected sqlite3_value objects may only be used as arguments
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to <a href="../c3ref/result_blob.html">sqlite3_result_value()</a>, <a href="../c3ref/bind_blob.html">sqlite3_bind_value()</a>, and
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<a href="../c3ref/value_dup.html">sqlite3_value_dup()</a>.
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The <a href="../c3ref/value_blob.html">sqlite3_value_type()</a> family of
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interfaces require protected sqlite3_value objects.
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</p><div class='columns' style='columns: 17em auto;'>
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<ul style='padding-top:0;'>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_blob</a></li>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_bytes</a></li>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_bytes16</a></li>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_double</a></li>
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<li><a href='../c3ref/value_dup.html'>sqlite3_value_dup</a></li>
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<li><a href='../c3ref/value_dup.html'>sqlite3_value_free</a></li>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_frombind</a></li>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_int</a></li>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_int64</a></li>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_nochange</a></li>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_numeric_type</a></li>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_pointer</a></li>
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<li><a href='../c3ref/value_subtype.html'>sqlite3_value_subtype</a></li>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_text</a></li>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_text16</a></li>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_text16be</a></li>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_text16le</a></li>
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<li><a href='../c3ref/value_blob.html'>sqlite3_value_type</a></li>
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</ul>
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</div>
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</p>
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<p>See also lists of
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<a href="objlist.html">Objects</a>,
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<a href="constlist.html">Constants</a>, and
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<a href="funclist.html">Functions</a>.</p>
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