107 lines
5.7 KiB
HTML
107 lines
5.7 KiB
HTML
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="SQL conversion rules" />
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<meta name="abstract" content="When two strings are compared, one of the strings is first converted, if necessary, to the coded character set of the other string." />
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<meta name="description" content="When two strings are compared, one of the strings is first converted, if necessary, to the coded character set of the other string." />
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<title>SQL conversion rules</title>
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</head>
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<body id="rbagssqlconversrules"><a name="rbagssqlconversrules"><!-- --></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 conversion rules</h1>
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<div><p>When two strings are compared, one of the strings is first converted,
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if necessary, to the coded character set of the other string.</p>
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<p>Character conversion is necessary only if all of the following
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conditions are true:</p>
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<ul><li>The CCSIDs of the two strings are different.</li>
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<li>Neither CCSID is 65535.</li>
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<li>The string selected for conversion is neither null nor empty.</li>
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<li>The CCSID conversion selection table indicates that conversion is necessary.</li>
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</ul>
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<p>If one string has an SBCS CCSID and the other is the same type of operand
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and has a mixed data CCSID, the SBCS data character string is converted. Otherwise,
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the string selected for conversion depends on the type of each operand. The
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following table shows which operand is selected for conversion, given the
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operand types.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><thead align="left"><tr><th valign="top" id="d0e35">First operand</th>
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<th valign="top" id="d0e37">Column value (second operand)</th>
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<th valign="top" id="d0e39">Derived value (second operand)</th>
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<th valign="top" id="d0e41">Special register (second operand)</th>
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<th valign="top" id="d0e43">Constant (second operand)</th>
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<th valign="top" id="d0e45">Host variable (second operand)</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e35 ">Column value</td>
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<td valign="top" headers="d0e37 ">Second</td>
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<td valign="top" headers="d0e39 ">Second</td>
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<td valign="top" headers="d0e41 ">Second</td>
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<td valign="top" headers="d0e43 ">Second</td>
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<td valign="top" headers="d0e45 ">Second</td>
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</tr>
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<tr><td valign="top" headers="d0e35 ">Derived Value</td>
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<td valign="top" headers="d0e37 ">First</td>
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<td valign="top" headers="d0e39 ">Second</td>
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<td valign="top" headers="d0e41 ">Second</td>
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<td valign="top" headers="d0e43 ">Second</td>
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<td valign="top" headers="d0e45 ">Second</td>
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</tr>
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<tr><td valign="top" headers="d0e35 ">Special Register</td>
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<td valign="top" headers="d0e37 ">First</td>
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<td valign="top" headers="d0e39 ">First</td>
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<td valign="top" headers="d0e41 ">Second</td>
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<td valign="top" headers="d0e43 ">Second</td>
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<td valign="top" headers="d0e45 ">Second</td>
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</tr>
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<tr><td valign="top" headers="d0e35 ">Constant</td>
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<td valign="top" headers="d0e37 ">First</td>
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<td valign="top" headers="d0e39 ">First</td>
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<td valign="top" headers="d0e41 ">First</td>
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<td valign="top" headers="d0e43 ">Second</td>
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<td valign="top" headers="d0e45 ">Second</td>
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</tr>
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<tr><td valign="top" headers="d0e35 ">Host Variable</td>
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<td valign="top" headers="d0e37 ">First</td>
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<td valign="top" headers="d0e39 ">First</td>
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<td valign="top" headers="d0e41 ">First</td>
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<td valign="top" headers="d0e43 ">First</td>
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<td valign="top" headers="d0e45 ">Second</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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<p>A host variable containing data in a foreign encoding scheme is always
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effectively converted to the native encoding scheme before it is used in any
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operation. The previous rules are based on the assumption that
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this conversion has already occurred.</p>
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<p>An error occurs if a character of the string cannot be converted or the
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CCSID Conversion Selection Table is used but does not contain any information
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about the pair of CCSIDs. A warning occurs if a character of the string is
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converted to the substitution character.</p>
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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="rbagssqlanddbchars.htm" title="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.">SQL and DBCS</a></div>
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</div>
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</div>
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</body>
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