95 lines
5.8 KiB
HTML
95 lines
5.8 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta name="DC.Title" content="Use user-defined distinct types (UDT)" />
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<meta name="abstract" content="A user-defined distinct type is a mechanism that allows you to extend DB2 capabilities beyond the built-in data types available." />
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<meta name="description" content="A user-defined distinct type is a mechanism that allows you to extend DB2 capabilities beyond the built-in data types available." />
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<meta name="DC.subject" content="data types, user-defined, UDTs (User-defined types), why use UDTs" />
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<meta name="keywords" content="data types, user-defined, UDTs (User-defined types), why use UDTs" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Use user-defined distinct types (UDT)</title>
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</head>
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<body id="rbafyuddt"><a name="rbafyuddt"><!-- --></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 user-defined distinct types (UDT)</h1>
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<div><p>A user-defined distinct type is a mechanism that allows you to
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extend DB2<sup>®</sup> capabilities
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beyond the built-in data types available.</p>
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<p> User-defined distinct types enable you to define new data types to DB2 which
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gives you considerable power since you are no longer restricted to using the
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system-supplied built-in data types to model your business and capture the
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semantics of your data. Distinct data types allow you to map on a one-to-one
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basis to existing database types.</p>
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<p>These benefits are associated with UDTs: </p>
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<ul><li><strong>Extensibility</strong>. <p>By defining new types, you can indefinitely
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increase the set of types provided by DB2 to support your applications. </p>
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</li>
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<li><strong>Flexibility</strong>. <p>You can specify any semantics and behavior for
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your new type by using user-defined functions (UDFs) to augment the diversity
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of the types available in the system. </p>
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</li>
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<li><strong>Consistent behavior</strong>. <p>Strong typing insures that your UDTs
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will behave appropriately. It guarantees that only functions defined on your
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UDT can be applied to instances of the UDT. </p>
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</li>
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<li><strong>Encapsulation</strong>. <p>The behavior of your UDTs is restricted by
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the functions and operators that can be applied on them. This provides flexibility
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in the implementation since running applications do not depend on the internal
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representation that you chose for your type. </p>
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</li>
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<li><strong>Extensible behavior</strong>. <p>The definition of user-defined functions
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on types can augment the functionality provided to manipulate your UDT at
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any time. </p>
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</li>
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<li><strong>Foundation for object-oriented extensions</strong>. <p>UDTs are the foundation
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for most object-oriented features. They represent the most important step
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toward object-oriented extensions. </p>
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</li>
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</ul>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="rbafydefudt.htm">Define a UDT</a></strong><br />
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UDTs are defined with a CREATE DISTINCT TYPE statement.</li>
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<li class="ulchildlink"><strong><a href="rbafydetab.htm">Define tables with UDTs</a></strong><br />
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After you have defined several UDTs, you can start defining tables with columns whose types are UDTs.</li>
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<li class="ulchildlink"><strong><a href="rbafymanudt.htm">Manipulate UDTs</a></strong><br />
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One of the most important concepts associated with UDTs is <em>strong
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typing</em>. Strong typing guarantees that only functions and operators defined
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on the UDT can be applied to its instances.</li>
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<li class="ulchildlink"><strong><a href="rbafyexampudt.htm">Examples: Use UDTs</a></strong><br />
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These are examples of using UDTs.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rbafyusoocap.htm" title="Most data types, such as INTEGER and CHARACTER, do not have any special processing characteristics. However, there are a few data types that require special functions or locators in order to use them.">Process special data types</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="rbafyusrdeftype.htm" title="A user-defined type is a distinct data type that users can define independently of those supplied by the database management system.">User-defined types</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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