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+<!-- keywords: sqlite3_create_collation sqlite3_create_collation16 sqlite3_create_collation_v2 -->
+<div class=nosearch>
+<a href="intro.html"><h2>SQLite C Interface</h2></a>
+<h2>Define New Collating Sequences</h2>
+</div>
+<blockquote><pre>
+int sqlite3_create_collation(
+ sqlite3*,
+ const char *zName,
+ int eTextRep,
+ void *pArg,
+ int(*xCompare)(void*,int,const void*,int,const void*)
+);
+int sqlite3_create_collation_v2(
+ sqlite3*,
+ const char *zName,
+ int eTextRep,
+ void *pArg,
+ int(*xCompare)(void*,int,const void*,int,const void*),
+ void(*xDestroy)(void*)
+);
+int sqlite3_create_collation16(
+ sqlite3*,
+ const void *zName,
+ int eTextRep,
+ void *pArg,
+ int(*xCompare)(void*,int,const void*,int,const void*)
+);
+</pre></blockquote>
+<p>
+These functions add, remove, or modify a <a href="../datatype3.html#collation">collation</a> associated
+with the <a href="../c3ref/sqlite3.html">database connection</a> specified as the first argument.</p>
+
+<p>The name of the collation is a UTF-8 string
+for sqlite3_create_collation() and sqlite3_create_collation_v2()
+and a UTF-16 string in native byte order for sqlite3_create_collation16().
+Collation names that compare equal according to <a href="../c3ref/stricmp.html">sqlite3_strnicmp()</a> are
+considered to be the same name.</p>
+
+<p>The third argument (eTextRep) must be one of the constants:
+<ul>
+<li> <a href="../c3ref/c_any.html">SQLITE_UTF8</a>,
+<li> <a href="../c3ref/c_any.html">SQLITE_UTF16LE</a>,
+<li> <a href="../c3ref/c_any.html">SQLITE_UTF16BE</a>,
+<li> <a href="../c3ref/c_any.html">SQLITE_UTF16</a>, or
+<li> <a href="../c3ref/c_any.html">SQLITE_UTF16_ALIGNED</a>.
+</ul>
+The eTextRep argument determines the encoding of strings passed
+to the collating function callback, xCompare.
+The <a href="../c3ref/c_any.html">SQLITE_UTF16</a> and <a href="../c3ref/c_any.html">SQLITE_UTF16_ALIGNED</a> values for eTextRep
+force strings to be UTF16 with native byte order.
+The <a href="../c3ref/c_any.html">SQLITE_UTF16_ALIGNED</a> value for eTextRep forces strings to begin
+on an even byte address.</p>
+
+<p>The fourth argument, pArg, is an application data pointer that is passed
+through as the first argument to the collating function callback.</p>
+
+<p>The fifth argument, xCompare, is a pointer to the collating function.
+Multiple collating functions can be registered using the same name but
+with different eTextRep parameters and SQLite will use whichever
+function requires the least amount of data transformation.
+If the xCompare argument is NULL then the collating function is
+deleted. When all collating functions having the same name are deleted,
+that collation is no longer usable.</p>
+
+<p>The collating function callback is invoked with a copy of the pArg
+application data pointer and with two strings in the encoding specified
+by the eTextRep argument. The two integer parameters to the collating
+function callback are the length of the two strings, in bytes. The collating
+function must return an integer that is negative, zero, or positive
+if the first string is less than, equal to, or greater than the second,
+respectively. A collating function must always return the same answer
+given the same inputs. If two or more collating functions are registered
+to the same collation name (using different eTextRep values) then all
+must give an equivalent answer when invoked with equivalent strings.
+The collating function must obey the following properties for all
+strings A, B, and C:</p>
+
+<p><ol>
+<li> If A==B then B==A.
+<li> If A==B and B==C then A==C.
+<li> If A&lt;B THEN B&gt;A.
+<li> If A&lt;B and B&lt;C then A&lt;C.
+</ol></p>
+
+<p>If a collating function fails any of the above constraints and that
+collating function is registered and used, then the behavior of SQLite
+is undefined.</p>
+
+<p>The sqlite3_create_collation_v2() works like sqlite3_create_collation()
+with the addition that the xDestroy callback is invoked on pArg when
+the collating function is deleted.
+Collating functions are deleted when they are overridden by later
+calls to the collation creation functions or when the
+<a href="../c3ref/sqlite3.html">database connection</a> is closed using <a href="../c3ref/close.html">sqlite3_close()</a>.</p>
+
+<p>The xDestroy callback is <u>not</u> called if the
+sqlite3_create_collation_v2() function fails. Applications that invoke
+sqlite3_create_collation_v2() with a non-NULL xDestroy argument should
+check the return code and dispose of the application data pointer
+themselves rather than expecting SQLite to deal with it for them.
+This is different from every other SQLite interface. The inconsistency
+is unfortunate but cannot be changed without breaking backwards
+compatibility.</p>
+
+<p>See also: <a href="../c3ref/collation_needed.html">sqlite3_collation_needed()</a> and <a href="../c3ref/collation_needed.html">sqlite3_collation_needed16()</a>.
+</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>
+