150 lines
8.7 KiB
HTML
150 lines
8.7 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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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta name="DC.Type" content="reference" />
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<meta name="DC.Title" content="Allowable conversions" />
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<meta name="abstract" content="When you change the data type of an existing column, the old and new attributes must be compatible." />
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<meta name="description" content="When you change the data type of an existing column, the old and new attributes must be compatible." />
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<meta name="DC.subject" content="ALTER TABLE statement, data types, allowable conversions" />
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<meta name="keywords" content="ALTER TABLE statement, data types, allowable conversions" />
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<meta name="DC.Relation" scheme="URI" content="rbafyalter.htm" />
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<meta name="DC.Relation" scheme="URI" content="rbafychgcol.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Format" content="XHTML" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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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>Allowable conversions</title>
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</head>
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<body id="rbafyallowable"><a name="rbafyallowable"><!-- --></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">Allowable conversions</h1>
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<div><p>When you change the data type of an existing column, the old and
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new attributes must be compatible. </p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" width="100%" frame="border" border="1" rules="all"><caption>Table 1. Allowable conversions</caption><thead align="left"><tr><th align="left" valign="bottom" width="50%" id="d0e34">FROM data type</th>
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<th align="left" valign="bottom" width="50%" id="d0e36">TO data type</th>
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</tr>
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</thead>
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<tbody><tr><td align="left" valign="top" width="50%" headers="d0e34 ">Decimal</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">Numeric</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">Decimal</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">Bigint, Integer, Smallint</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">Decimal</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">Float</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">Numeric</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">Decimal</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">Numeric</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">Bigint, Integer, Smallint</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">Numeric</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">Float</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">Bigint, Integer, Smallint</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">Decimal</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">Bigint, Integer, Smallint</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">Numeric</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">Bigint, Integer, Smallint</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">Float</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">Float</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">Numeric</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">Float</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">Bigint, Integer, Smallint</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">Character</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">DBCS-open</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">Character</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">UCS-2 or UTF-16 graphic</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">DBCS-open</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">Character</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">DBCS-open</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">UCS-2 or UTF-16 graphic</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">DBCS-either</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">Character</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">DBCS-either</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">DBCS-open</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">DBCS-either</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">UCS-2 or UTF-16 graphic</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">DBCS-only</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">DBCS-open</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">DBCS-only</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">DBCS graphic</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">DBCS-only</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">UCS-2 or UTF-16 graphic</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">DBCS graphic</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">UCS-2 or UTF-16 graphic</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">UCS-2 or UTF-16 graphic</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">Character</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">UCS-2 or UTF-16 graphic</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">DBCS-open</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">UCS-2 or UTF-16 graphic</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">DBCS graphic</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">distinct type</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">source type</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e34 ">source type</td>
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<td align="left" valign="top" width="50%" headers="d0e36 ">distinct type</td>
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</tr>
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</tbody>
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</table>
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</div>
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<div class="section"><p>When modifying an existing column, only the attributes that you
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specify will be changed. All other attributes will remain unchanged. For
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example, given the following table definition: </p>
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<pre> <strong>CREATE TABLE</strong> EX1 (COL1 <strong>CHAR</strong>(10) <strong>DEFAULT</strong> 'COL1',
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COL2 <strong>VARCHAR</strong>(20) <strong>ALLOCATE</strong>(10) <strong>CCSID</strong> 937,
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COL3 <strong>VARGRAPHIC</strong>(20) <strong>ALLOCATE</strong>(10)
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<strong>NOT NULL WITH DEFAULT</strong>)</pre>
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</div>
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<div class="section"><p>After running the following ALTER TABLE statement: </p>
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<pre> <strong>ALTER TABLE</strong> EX1 <strong>ALTER COLUMN</strong> COL2 <strong>SET DATA TYPE VARCHAR</strong>(30)
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<strong>ALTER COLUMN</strong> COL3 <strong>DROP NOT NULL</strong></pre>
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</div>
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<div class="section"><p>COL2 still has an allocated length of 10 and CCSID 937, and COL3
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still has an allocated length of 10.</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="rbafyalter.htm" title="Changing the definition of a table allows you to add new columns, change an existing column definition (change its length, default value, and so on), drop existing columns, and add and remove constraints.">Change a table definition</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="rbafychgcol.htm" title="You can change a column definition in a table using the ALTER COLUMN clause of the ALTER TABLE statement.">Change a column</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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