68 lines
4.5 KiB
HTML
68 lines
4.5 KiB
HTML
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<meta name="DC.Title" content="Example: Use UDFs to query instances of UDTs" />
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<meta name="abstract" content="Suppose you need to know how much e-mail was sent by a specific customer regarding customer orders and you have the e-mail address of your customers in the customers table." />
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<title>Example: Use UDFs to query instances of UDTs</title>
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<body id="rbafyexpudf"><a name="rbafyexpudf"><!-- --></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">Example: Use UDFs to query instances of UDTs</h1>
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<div><p>Suppose you need to know how much e-mail was sent by a specific
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customer regarding customer orders and you have the e-mail address of your
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customers in the customers table.</p>
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<div class="section"><p>The statement is as follows:</p>
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<pre> <strong>SELECT COUNT</strong> (*)
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<strong>FROM</strong> ELECTRONIC_MAIL AS EMAIL, CUSTOMERS
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<strong>WHERE</strong> SUBJECT (EMAIL.MESSAGE) = 'customer order'
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<strong>AND</strong> CUSTOMERS.EMAIL_ADDRESS = SENDER (EMAIL.MESSAGE)
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<strong>AND</strong> CUSTOMERS.NAME = 'Customer X'</pre>
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</div>
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<div class="section"><p>You have used the UDFs defined on the UDT in this SQL query since
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they are the only means to manipulate the UDT. In this sense, your UDT e-mail
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is completely encapsulated. Its internal representation and structure are
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hidden and can only be manipulated by the defined UDFs. These UDFs know how
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to interpret the data without the need to expose its representation.</p>
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</div>
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<div class="section"><p>Suppose you need to know the details of all the e-mail your company
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received in 1994 that had to do with the performance of your products in the
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marketplace.</p>
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<pre> <strong>SELECT</strong> SENDER (MESSAGE), SENDING_DATE (MESSAGE), SUBJECT (MESSAGE)
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<strong>FROM</strong> ELECTRONIC_MAIL
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<strong>WHERE</strong> CONTAINS (MESSAGE,
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'"performance" <strong>AND</strong> "products" <strong>AND</strong> "marketplace"') = 1 </pre>
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</div>
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<div class="section"><p>You have used the <samp class="codeph">contains</samp> UDF that is capable
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of analyzing the contents of the message searching for relevant keywords or
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synonyms.</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="rbafyexampcomplex.htm" title="The following examples show how you can use user-defined types (UDTs), user-defined functions (UDFs), and large objects (LOBs) together in complex applications.">Examples of using UDTs, UDFs, and LOBs</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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