52 lines
3.4 KiB
HTML
52 lines
3.4 KiB
HTML
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<meta name="DC.Title" content="How can the host variable type in WHERE clauses affect performance?" />
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<meta name="abstract" content="One potential source of performance degradation on an iSeries server is the client's use in a C program of a floating point variable for a comparison in the WHERE clause of a SELECT statement." />
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<title>How can the host variable type in WHERE clauses affect performance?</title>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">How can the host variable type in WHERE clauses affect performance?</h1>
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<div><p>One potential source of performance degradation on an iSeries™ server
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is the client's use in a C program of a floating point variable for a comparison
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in the WHERE clause of a SELECT statement.</p>
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<div class="section"><p>If the operating system has to do a conversion of the data for
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that column, that will prevent it from being able to use an index on that
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column. You should always try to use the same type for columns, literals,
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and host variables used in a comparison. If the column in the database is
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defined as packed or zoned decimal, and the host variable is of some other
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type, that can present a problem in C.</p>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rbal1xplat.htm" title="This topic collection concentrates on describing iSeries support for distributed relational databases in a network of iSeries servers (a like environment).">User FAQs</a></div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="../rzajq/progtech.htm">Programming techniques for database performance</a></div>
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