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			<h1>common_schema</h1> <strong>2.2</strong> documentation
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				<h2><a href="crc64.html">crc64</a></h2>	
<h3>NAME</h3>
crc64(): Return a 64 bit CRC of given input, as unsigned big integer.
<h3>TYPE</h3>
Function

<h3>DESCRIPTION</h3>
<p>
	This function complements MySQL's crc32() function,	which results with poor distribution
	on large number of values.
	The <i>crc64()</i> algorithm relies on <strong>MD5</strong> as underlying mechanism. 
</p>
<p>
  While input <strong>data</strong> is textual, any type can be passed in, due to SQL's implicit casting nature.
</p>
<p>
	This code is based on the idea presented in the book
	<i>High Performance MySQL, 2nd Edition</i>, By Baron Schwartz et al., published by O'REILLY
</p>

<h3>SYNOPSIS</h3>
<p>
<blockquote><pre>crc64(data LONGTEXT CHARSET utf8) 
  RETURNS BIGINT UNSIGNED</pre></blockquote>
</p>
<p>
  Input:
  <ul>
    <li><strong>data</strong>: data to run CRC on. This can be textual, numeric, temporal, or any other type
      that can be implicitly converted to <strong>TEXT</strong>.</li>
  </ul>
</p>

<h3>EXAMPLES</h3>
	<p>
		Calculate 64 bit CRC for some text:
	</p>
	<blockquote><pre>mysql&gt; SELECT common_schema.crc64('mysql') AS crc64;
+---------------------+
| crc64               |
+---------------------+
| 9350511318824990686 |
+---------------------+
</pre></blockquote>

<h3>ENVIRONMENT</h3>
MySQL 5.1 or newer

<h3>SEE ALSO</h3>
<a href="query_checksum.html">query_checksum()</a>,
<a href="random_hash.html">random_hash()</a>

<h3>AUTHOR</h3>
Shlomi Noach
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