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206 lines
11 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<meta http-equiv="content-type" content="text/html; charset=UTF-8">
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<title>Registers a "regular" User Defined Function for use in SQL statements</title>
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</head>
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<body class="docs"><div id="layout">
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<div id="layout-content"><div id="function.sqlite-create-function" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">sqlite_create_function</h1>
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<h1 class="refname">SQLiteDatabase::createFunction</h1>
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<p class="verinfo">(PHP 5 < 5.4.0, sqlite >= 1.0.0)</p><p class="refpurpose"><span class="refname">sqlite_create_function</span> -- <span class="refname">SQLiteDatabase::createFunction</span> — <span class="dc-title">
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Registers a "regular" User Defined Function for use in SQL statements
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</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.sqlite-create-function-description">
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<h3 class="title">说明</h3>
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<div class="methodsynopsis dc-description">
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<span class="methodname"><strong>sqlite_create_function</strong></span>
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( <span class="methodparam"><span class="type">resource</span> <code class="parameter">$dbhandle</code></span>
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, <span class="methodparam"><span class="type">string</span> <code class="parameter">$function_name</code></span>
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, <span class="methodparam"><span class="type"><a href="language.types.callable.html" class="type callable">callable</a></span> <code class="parameter">$callback</code></span>
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[, <span class="methodparam"><span class="type">int</span> <code class="parameter">$num_args</code><span class="initializer"> = -1</span></span>
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] ) : <span class="type"><span class="type void">void</span></span></div>
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<p class="para rdfs-comment">面向对象风格 (method):</p>
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<div class="methodsynopsis dc-description">
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<span class="modifier">public</span> <span class="methodname"><strong>SQLiteDatabase::createFunction</strong></span>
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( <span class="methodparam"><span class="type">string</span> <code class="parameter">$function_name</code></span>
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, <span class="methodparam"><span class="type"><a href="language.types.callable.html" class="type callable">callable</a></span> <code class="parameter">$callback</code></span>
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[, <span class="methodparam"><span class="type">int</span> <code class="parameter">$num_args</code><span class="initializer"> = -1</span></span>
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] ) : <span class="type"><span class="type void">void</span></span></div>
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<p class="para rdfs-comment">
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<span class="function"><strong>sqlite_create_function()</strong></span> allows you to register a PHP
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function with SQLite as an <acronym title="User Defined Functions">UDF</acronym> (User Defined
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Function), so that it can be called from within your SQL statements.
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</p>
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<p class="para">
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The UDF can be used in any SQL statement that can call functions, such as
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SELECT and UPDATE statements and also in triggers.
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</p>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.sqlite-create-function-parameters">
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<h3 class="title">参数</h3>
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<p class="para">
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<dl>
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<dt>
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<code class="parameter">dbhandle</code></dt>
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<dd>
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<p class="para">
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The SQLite Database resource; returned from <span class="function"><a href="sqlite_open.html" class="function">sqlite_open()</a></span>
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when used procedurally. This parameter is not required
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when using the object-oriented method.
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</p>
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</dd>
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<dt>
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<code class="parameter">function_name</code></dt>
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<dd>
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<p class="para">
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The name of the function used in SQL statements.
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</p>
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</dd>
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<dt>
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<code class="parameter">callback</code></dt>
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<dd>
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<p class="para">
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Callback function to handle the defined SQL function.
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</p>
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<blockquote class="note"><p><strong class="note">Note</strong>:
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<span class="simpara">
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Callback functions should return a type understood by SQLite (i.e.
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<a href="language.types.intro.html" class="link">scalar type</a>).
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</span>
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</p></blockquote>
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</dd>
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<dt>
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<code class="parameter">num_args</code></dt>
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<dd>
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<p class="para">
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Hint to the SQLite parser if the callback function accepts a
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predetermined number of arguments.
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</p>
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</dd>
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</dl>
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</p>
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<blockquote class="note"><p><strong class="note">Note</strong>: <span class="simpara">为兼容其他数据库扩展(比如 MySQL)，支持两种可替代的语法。推荐第一种格式，函数的第一个参数是<code class="parameter">dbhandle</code>。</span></p></blockquote>
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</div>
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<div class="refsect1 returnvalues" id="refsect1-function.sqlite-create-function-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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没有返回值。
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</p>
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</div>
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<div class="refsect1 examples" id="refsect1-function.sqlite-create-function-examples">
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<h3 class="title">范例</h3>
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<p class="para">
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<div class="example" id="example-2531">
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<p><strong>Example #1 <span class="function"><strong>sqlite_create_function()</strong></span> example</strong></p>
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<div class="example-contents">
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<div class="phpcode"><pre><span style="color: #000000">
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<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">md5_and_reverse</span><span style="color: #007700">(</span><span style="color: #0000BB">$string</span><span style="color: #007700">) <br />{<br /> return </span><span style="color: #0000BB">strrev</span><span style="color: #007700">(</span><span style="color: #0000BB">md5</span><span style="color: #007700">(</span><span style="color: #0000BB">$string</span><span style="color: #007700">));<br />}<br /><br />if (</span><span style="color: #0000BB">$dbhandle </span><span style="color: #007700">= </span><span style="color: #0000BB">sqlite_open</span><span style="color: #007700">(</span><span style="color: #DD0000">'mysqlitedb'</span><span style="color: #007700">, </span><span style="color: #0000BB">0666</span><span style="color: #007700">, </span><span style="color: #0000BB">$sqliteerror</span><span style="color: #007700">)) {<br /> <br /> </span><span style="color: #0000BB">sqlite_create_function</span><span style="color: #007700">(</span><span style="color: #0000BB">$dbhandle</span><span style="color: #007700">, </span><span style="color: #DD0000">'md5rev'</span><span style="color: #007700">, </span><span style="color: #DD0000">'md5_and_reverse'</span><span style="color: #007700">, </span><span style="color: #0000BB">1</span><span style="color: #007700">);<br /> <br /> </span><span style="color: #0000BB">$sql </span><span style="color: #007700">= </span><span style="color: #DD0000">'SELECT md5rev(filename) FROM files'</span><span style="color: #007700">;<br /> </span><span style="color: #0000BB">$rows </span><span style="color: #007700">= </span><span style="color: #0000BB">sqlite_array_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$dbhandle</span><span style="color: #007700">, </span><span style="color: #0000BB">$sql</span><span style="color: #007700">);<br />} else {<br /> echo </span><span style="color: #DD0000">'Error opening sqlite db: ' </span><span style="color: #007700">. </span><span style="color: #0000BB">$sqliteerror</span><span style="color: #007700">;<br /> exit;<br />}<br /></span><span style="color: #0000BB">?></span>
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</span>
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</pre></div>
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</div>
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</div>
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</p>
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<p class="para">
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In this example, we have a function that calculates the md5 sum of a
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string, and then reverses it. When the SQL statement executes, it
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returns the value of the filename transformed by our function. The data
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returned in <code class="parameter">$rows</code> contains the processed result.
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</p>
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<p class="para">
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The beauty of this technique is that you do not need to process the
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result using a <a href="control_structures.foreach.html" class="link">foreach</a> loop after you have queried for the data.
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</p>
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<p class="para">
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PHP registers a special function named <em>php</em> when the
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database is first opened. The php function can be used to call any PHP
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function without having to register it first.
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</p>
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<p class="para">
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<div class="example" id="example-2532">
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<p><strong>Example #2 Example of using the PHP function</strong></p>
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<div class="example-contents">
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<div class="phpcode"><pre><span style="color: #000000">
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<span style="color: #0000BB"><?php<br />$rows </span><span style="color: #007700">= </span><span style="color: #0000BB">sqlite_array_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$dbhandle</span><span style="color: #007700">, </span><span style="color: #DD0000">"SELECT php('md5', filename) from files"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
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</span>
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</pre></div>
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</div>
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<div class="example-contents"><p>
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This example will call the <span class="function"><a href="md5.html" class="function">md5()</a></span> on each
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<em>filename</em> column in the database and return the result
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into <code class="parameter">$rows</code>
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</p></div>
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</div>
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</p>
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<blockquote class="note"><p><strong class="note">Note</strong>:
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<p class="para">
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For performance reasons, PHP will not automatically encode/decode binary
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data passed to and from your UDF's. You need to manually encode/decode
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the parameters and return values if you need to process binary data in
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this way. Take a look at <span class="function"><a href="sqlite_udf_encode_binary.html" class="function">sqlite_udf_encode_binary()</a></span>
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and <span class="function"><a href="sqlite_udf_decode_binary.html" class="function">sqlite_udf_decode_binary()</a></span> for more details.
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</p>
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</p></blockquote>
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<div class="tip"><strong class="tip">Tip</strong>
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<p class="para">
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It is not recommended to use UDF's to handle processing of
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binary data, unless high performance is not a key requirement of your
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application.
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</p>
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</div>
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<div class="tip"><strong class="tip">Tip</strong>
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<p class="para">
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You can use <span class="function"><strong>sqlite_create_function()</strong></span> and
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<span class="function"><a href="sqlite_create_aggregate.html" class="function">sqlite_create_aggregate()</a></span> to override SQLite native
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SQL functions.
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</p>
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</div>
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</div>
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<div class="refsect1 seealso" id="refsect1-function.sqlite-create-function-seealso">
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<h3 class="title">参见</h3>
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<p class="para">
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<ul class="simplelist">
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<li class="member"><span class="function"><a href="sqlite_create_aggregate.html" class="function" rel="rdfs-seeAlso">sqlite_create_aggregate()</a> - Register an aggregating UDF for use in SQL statements</span></li>
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</ul>
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</p>
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</div>
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</div></div></div></body></html> |