109 lines
6.9 KiB
HTML
109 lines
6.9 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="concept" />
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<meta name="DC.Title" content="SQL and DBCS" />
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<meta name="abstract" content="The basic symbols of keywords and operators in the SQL language are single-byte characters that are part of all character sets supported by the IBM relational database products. Characters of the language are classified as letters, digits, or special characters." />
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<meta name="description" content="The basic symbols of keywords and operators in the SQL language are single-byte characters that are part of all character sets supported by the IBM relational database products. Characters of the language are classified as letters, digits, or special characters." />
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<meta name="DC.Relation" scheme="URI" content="rbagsdesigndbcsapps.htm" />
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<meta name="DC.Relation" scheme="URI" content="rbagssqlgraphstrngcons.htm" />
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<meta name="DC.Relation" scheme="URI" content="rbagssqlasgncompdbcs.htm" />
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<meta name="DC.Relation" scheme="URI" content="rbagssqlconversrules.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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<!-- 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>SQL and DBCS</title>
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</head>
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<body id="rbagssqlanddbchars"><a name="rbagssqlanddbchars"><!-- --></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">SQL and DBCS</h1>
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<div><p>The basic symbols of keywords and operators in the SQL language
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are single-byte characters that are part of all character sets supported by
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the IBM<sup>®</sup> relational
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database products. Characters of the language are classified as letters, digits,
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or special characters.</p>
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<div class="section"><h4 class="sectiontitle">SQL host identifiers and double-byte characters</h4><p>A
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host-identifier is a name declared in the host program. The rules for forming
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a host-identifier are the rules of the host language, except that DBCS characters
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cannot be used.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">SQL character subtypes and double-byte characters</h4><p>Each character string is further defined as follows:</p>
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<ul><li><span class="uicontrol">Bit data:</span> <p>Data that is not associated with a
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coded character set and is never converted. The CCSID for bit data is 65535.</p>
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</li>
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<li><span class="uicontrol">SBCS data:</span> <p>Data in which every character is
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represented by a single byte. Each SBCS data character string has an associated
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CCSID. If necessary, an SBCS data character string is converted before it
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is used in an operation with a character string that has a different CCSID.</p>
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</li>
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<li><span class="uicontrol">Mixed data:</span> <p>Data that contains a mixture of
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characters from a single-byte character set (SBCS) and a double-byte character
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set (DBCS). Each mixed data character string has an associated CCSID. If necessary,
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a mixed data character string is converted before an operation
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with a character string that has a different CCSID. If mixed data contains
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a DBCS character, it cannot be converted to SBCS data.</p>
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</li>
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</ul>
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<p>The database manager does not recognize subclasses of double-byte
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characters, and it does not assign any specific meaning to particular double-byte
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codes. However, if you choose to use mixed data, then two single-byte EBCDIC
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codes are given special meanings:</p>
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<ul><li>X'0E', the shift-out character, is used to mark the beginning of a sequence
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of double-byte codes.</li>
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<li>X'0F', the shift-in character, is used to mark the end of a sequence of
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double-byte codes.</li>
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</ul>
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<p>In order for the database manager to recognize double-byte characters
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in a mixed data character string, the following condition must be met:</p>
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<ul><li>Within the string, the double-byte characters must be enclosed between
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paired shift-out and shift-in characters. <p>The pairing is detected as the
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string is read from left to right. The code X'0E' is recognized as a shift
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out character if X'0F' occurs later; otherwise, it is invalid. The first X'0F'
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following the X'0E' that is on a double-byte boundary is the paired shift-in
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character. Any X'0F' that is not on a double-byte boundary is not recognized.</p>
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<p>There
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must be an even number of bytes between the paired characters, and each pair
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of bytes is considered to be a double-byte character. There can be more than
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one set of paired shift-out and shift-in characters in the string.</p>
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</li>
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</ul>
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<p>The length of a mixed data character string is its total number of
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bytes, counting two bytes for each double-byte character and one byte for
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each shift-out or shift-in character.</p>
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<p>When the job CCSID indicates that
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DBCS is allowed, CREATE TABLE will create character columns as DBCS-Open fields,
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unless FOR BIT DATA, FOR SBCS DATA, or an SBCS CCSID is specified. The SQL
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user will see these as character fields, but the system database support will
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see them as DBCS-Open fields.</p>
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</div>
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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="rbagssqlgraphstrngcons.htm">SQL graphic strings</a></strong><br />
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A graphic string is a sequence of double-byte characters that do not include shift-out or shift-in characters.</li>
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<li class="ulchildlink"><strong><a href="rbagssqlasgncompdbcs.htm">SQL assignments and comparisons</a></strong><br />
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The basic operations of SQL are assignment and comparison.</li>
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<li class="ulchildlink"><strong><a href="rbagssqlconversrules.htm">SQL conversion rules</a></strong><br />
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When two strings are compared, one of the strings is first converted, if necessary, to the coded character set of the other string.</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="rbagsdesigndbcsapps.htm" title="Design your application programs for processing double-byte data in the same way you design application programs for processing alphanumeric data.">Develop applications that process DBCS data</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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