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<a href="intro.html"><h2>SQLite C Interface</h2></a><h2>Obtaining SQL Function Parameter Values</h2><blockquote><pre>const void *sqlite3_value_blob(sqlite3_value*);
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int sqlite3_value_bytes(sqlite3_value*);
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int sqlite3_value_bytes16(sqlite3_value*);
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double sqlite3_value_double(sqlite3_value*);
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int sqlite3_value_int(sqlite3_value*);
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sqlite3_int64 sqlite3_value_int64(sqlite3_value*);
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const unsigned char *sqlite3_value_text(sqlite3_value*);
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const void *sqlite3_value_text16(sqlite3_value*);
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const void *sqlite3_value_text16le(sqlite3_value*);
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const void *sqlite3_value_text16be(sqlite3_value*);
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int sqlite3_value_type(sqlite3_value*);
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int sqlite3_value_numeric_type(sqlite3_value*);
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</pre></blockquote><p>
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The C-language implementation of SQL functions and aggregates uses
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this set of interface routines to access the parameter values on
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the function or aggregate.</p>
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<p>The xFunc (for scalar functions) or xStep (for aggregates) parameters
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to <a href="../c3ref/create_function.html">sqlite3_create_function()</a> and <a href="../c3ref/create_function.html">sqlite3_create_function16()</a>
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define callbacks that implement the SQL functions and aggregates.
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The 3rd parameter to these callbacks is an array of pointers to
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<a href="../c3ref/value.html">protected sqlite3_value</a> objects. There is one <a href="../c3ref/value.html">sqlite3_value</a> object for
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each parameter to the SQL function. These routines are used to
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extract values from the <a href="../c3ref/value.html">sqlite3_value</a> objects.</p>
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<p>These routines work only with <a href="../c3ref/value.html">protected sqlite3_value</a> objects.
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Any attempt to use these routines on an <a href="../c3ref/value.html">unprotected sqlite3_value</a>
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object results in undefined behavior.</p>
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<p>These routines work just like the corresponding <a href="../c3ref/column_blob.html">column access functions</a>
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except that these routines take a single <a href="../c3ref/value.html">protected sqlite3_value</a> object
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pointer instead of a <a href="../c3ref/stmt.html">sqlite3_stmt*</a> pointer and an integer column number.</p>
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<p>The sqlite3_value_text16() interface extracts a UTF-16 string
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in the native byte-order of the host machine. The
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sqlite3_value_text16be() and sqlite3_value_text16le() interfaces
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extract UTF-16 strings as big-endian and little-endian respectively.</p>
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<p>The sqlite3_value_numeric_type() interface attempts to apply
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numeric affinity to the value. This means that an attempt is
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made to convert the value to an integer or floating point. If
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such a conversion is possible without loss of information (in other
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words, if the value is a string that looks like a number)
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then the conversion is performed. Otherwise no conversion occurs.
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The <a href="../c3ref/c_blob.html">datatype</a> after conversion is returned.</p>
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<p>Please pay particular attention to the fact that the pointer returned
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from <a href="../c3ref/value_blob.html">sqlite3_value_blob()</a>, <a href="../c3ref/value_blob.html">sqlite3_value_text()</a>, or
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<a href="../c3ref/value_blob.html">sqlite3_value_text16()</a> can be invalidated by a subsequent call to
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<a href="../c3ref/value_blob.html">sqlite3_value_bytes()</a>, <a href="../c3ref/value_blob.html">sqlite3_value_bytes16()</a>, <a href="../c3ref/value_blob.html">sqlite3_value_text()</a>,
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or <a href="../c3ref/value_blob.html">sqlite3_value_text16()</a>.</p>
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<p>These routines must be called from the same thread as
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the SQL function that supplied the <a href="../c3ref/value.html">sqlite3_value*</a> parameters.
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</p><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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