82 lines
5.6 KiB
HTML
82 lines
5.6 KiB
HTML
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<meta name="DC.Title" content="Use qualified function reference" />
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<meta name="abstract" content="If you use a qualified function reference, you restrict the search for a matching function to that schema." />
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<meta name="description" content="If you use a qualified function reference, you restrict the search for a matching function to that schema." />
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<title>Use qualified function reference </title>
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<body id="rbafyusquref"><a name="rbafyusquref"><!-- --></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 qualified function reference </h1>
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<div><p>If you use a qualified function reference, you restrict the search
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for a matching function to that schema.</p>
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<div class="section"><p>For example, you have the following statement:</p>
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<pre> <strong>SELECT</strong> PABLO.BLOOP(COLUMN1) <strong>FROM</strong> T </pre>
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</div>
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<div class="section"><p>Only the BLOOP functions in schema PABLO are considered. It does
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not matter that user SERGE has defined a BLOOP function, or whether there
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is a built-in BLOOP function. Now suppose that user PABLO has defined two
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BLOOP functions in his schema:</p>
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<pre> <strong>CREATE FUNCTION</strong> BLOOP (<strong>INTEGER</strong>) <strong>RETURNS</strong> ...
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<strong>CREATE FUNCTION</strong> BLOOP (<strong>DOUBLE</strong>) <strong>RETURNS</strong> ...</pre>
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</div>
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<div class="section"><p>BLOOP is thus overloaded within the PABLO schema, and the function
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selection algorithm chooses the best BLOOP, depending on the data type of
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the argument, COLUMN1. In this case, both of the PABLO.BLOOPs take numeric
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arguments, and if COLUMN1 is not one of the numeric types, the statement
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will fail. On the other hand if COLUMN1 is either SMALLINT or INTEGER, function
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selection will resolve to the first BLOOP, while if COLUMN1 is DECIMAL or
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DOUBLE, the second BLOOP will be chosen. </p>
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</div>
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<div class="section"><p>Several points about this example:</p>
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</div>
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<div class="section"> <ol><li>It illustrates argument promotion. The first BLOOP is defined with an
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INTEGER parameter, yet you can pass it a SMALLINT argument. The function
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selection algorithm supports promotions among the built-in data types and DB2<sup>®</sup> performs
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the appropriate data value conversions.</li>
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<li>If for some reason you want to call the second BLOOP with a SMALLINT
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or INTEGER argument, you need to take an explicit action in your statement
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as follows: <pre> <strong>SELECT</strong> PABLO.BLOOP(<strong>DOUBLE</strong>(COLUMN1)) <strong>FROM</strong> T</pre>
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</li>
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<li>If you want to call the first BLOOP with a DECIMAL or DOUBLE argument,
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you have your choice of explicit actions, depending on your intent: <pre> <strong>SELECT</strong> PABLO.BLOOP(<strong>INTEGER</strong>(COLUMN1)) <strong>FROM</strong> T
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<strong>SELECT</strong> PABLO.BLOOP(<strong>FLOOR</strong>(COLUMN1)) <strong>FROM</strong> T </pre>
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</li>
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</ol>
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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="rbafyudfuudf.htm" title="Scalar and column UDFs can be called within an SQL statement almost everywhere that an expression is valid. Table UDFs can be called in the FROM clause of a SELECT. There are a few restrictions of UDF usage, however.">Use UDFs in SQL statements</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="rbafyuseunqualified.htm" title="You can use an unqualified function reference instead of a qualified function reference. In this case, DB2's search for a matching function normally uses the function path to qualify the reference.">Use unqualified function reference</a></div>
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<div><a href="rbafydefudt.htm" title="UDTs are defined with a CREATE DISTINCT TYPE statement.">Define a UDT</a></div>
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</div>
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</div>
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</body>
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</html>
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