67 lines
4.1 KiB
HTML
67 lines
4.1 KiB
HTML
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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="Change a column" />
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<meta name="abstract" content="You can change a column definition in a table using the ALTER COLUMN clause of the ALTER TABLE statement." />
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<meta name="description" content="You can change a column definition in a table using the ALTER COLUMN clause of the ALTER TABLE statement." />
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<meta name="DC.subject" content="ALTER TABLE statement, changing a column, column, changing definition" />
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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>Change a column</title>
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</head>
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<body id="rbafychgcol"><a name="rbafychgcol"><!-- --></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">Change a column</h1>
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<div><p>You can change a column definition in a table using the ALTER COLUMN
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clause of the ALTER TABLE statement.</p>
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<div class="section"><p>When you change the data type of an existing column, the old and
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new attributes must be compatible.
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You can always change a character, graphic, or binary column from fixed length
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to varying length or LOB; or from varying length or LOB to fixed length.</p>
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</div>
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<div class="section"><p>When you convert to a data type with a longer length, data will
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be padded with the appropriate pad character. When you convert to a data
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type with a shorter length, data may be lost due to truncation. An inquiry
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message prompts you to confirm the request.</p>
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</div>
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<div class="section"><p>If you have a column that does not allow the null value and you
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want to change it to now allow the null value, use the DROP NOT NULL clause.
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If you have a column that allows the null value and you want to prevent the
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use of null values, use the SET NOT NULL clause. If any of the existing values
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in that column are the null value, the ALTER TABLE will not be performed and
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an SQLCODE of -190 will result.</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="rbafyallowable.htm" title="When you change the data type of an existing column, the old and new attributes must be compatible.">Allowable conversions</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="../db2/rbafzmstatabl.htm">ALTER TABLE</a></div>
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</div>
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</div>
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</body>
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</html> |