71 lines
4.6 KiB
HTML
71 lines
4.6 KiB
HTML
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<meta name="DC.Type" content="reference" />
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<meta name="DC.Title" content="Use Extended Dynamic SQL" />
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<meta name="abstract" content="Use the ODBC call level interface to dynamically run your SQL statements." />
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<title>Use Extended Dynamic SQL</title>
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</head>
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<body id="useedsql"><a name="useedsql"><!-- --></a>
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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">Use Extended Dynamic <span class="keyword">SQL</span></h1>
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<div><p>Use the ODBC call level interface to dynamically run your SQL statements.</p>
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<div class="section"><p>Traditional <span class="keyword">SQL</span> interfaces
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used an embedded <span class="keyword">SQL</span> approach. <span class="keyword">SQL</span> statements were placed directly
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in an application's source code, along with high-level language statements
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written in C, COBOL, RPG, and other programming languages. The source code
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then was precompiled, which translated the <span class="keyword">SQL</span> statements
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into code that the subsequent compile step could process. This method sometimes
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was referred to as <strong>static <span class="keyword">SQL</span></strong>.
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One performance advantage to this approach is that <span class="keyword">SQL</span> statements
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were optimized in advance, rather than at runtime while the user was waiting.</p>
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</div>
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<div class="section"><p>ODBC, however, is a <strong>call level interface</strong> (CLI) that uses
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a different approach. Using a CLI, <span class="keyword">SQL</span> statements
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are passed to the database management system (DBMS) within a parameter of
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a runtime API. Because the text of the <span class="keyword">SQL</span> statement
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is never known until runtime, the optimization step must be performed each
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time an <span class="keyword">SQL</span> statement
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is run. This approach commonly is referred to as <strong>dynamic <span class="keyword">SQL</span></strong>.</p>
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</div>
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<div class="section"><p>The use of this feature (which is enabled by default) not only
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can improve response times, but can improve dramatically server utilization.
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This is because optimizing <span class="keyword">SQL</span> queries
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can be costly, and performing this step only once always is advantageous.
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This works well with a unique feature of DB2<sup>®</sup> UDB for iSeries™. Unlike other DBMSs, it ensures
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that statements which are stored in packages are kept up-to-date in terms
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of optimization, without administrator intervention. Even if a statement was
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prepared for the first time weeks or months ago, DB2 UDB for iSeries automatically regenerates the
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access plan when it determines that sufficient database changes require reoptimization.</p>
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</div>
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<div class="section"><p>For more information on packages and the types of SQL statements
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stored in them see <a href="../rzaii/rzaiimst38.htm">SQL
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packages</a>. </p>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaikodbcperfarch.htm" title="For the iSeries Access for Windows ODBC driver, all of the internal data flows between the client and the server are chained together, and transmit only when needed.">The performance architecture of the iSeries Access for Windows ODBC driver</a></div>
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</div>
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</div>
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</body>
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