105 lines
6.5 KiB
HTML
105 lines
6.5 KiB
HTML
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<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" lang="en-US" xml:lang="en-us">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="dc.language" scheme="rfc1766" content="en-us" />
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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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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<meta name="dc.date" scheme="iso8601" content="2005-09-19" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<meta name="keywords" content="description, SQLDA, application program, contents,
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SQLDA (SQL descriptor area), dynamic SQL, with SQLDA, obtaining information,
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prepared SQL statement, SQLDA provides information" />
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<title>SQLDA (SQL descriptor area)</title>
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<link rel="stylesheet" type="text/css" href="ibmidwb.css" />
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<link rel="stylesheet" type="text/css" href="ic.css" />
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</head>
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<body>
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<a id="Top_Of_Page" name="Top_Of_Page"></a><!-- Java sync-link -->
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<script language = "Javascript" src = "../rzahg/synch.js" type="text/javascript"></script>
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<a name="sqldda"></a>
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<h1 id="sqldda"><a href="rbafzmst02.htm#ToC_1496">Appendix D. SQLDA (SQL descriptor area)</a></h1><a id="idx3434" name="idx3434"></a><a id="idx3435" name="idx3435"></a><a id="idx3436" name="idx3436"></a><a id="idx3437" name="idx3437"></a>
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<p>An SQLDA is a set of variables that is used for execution of
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the SQL DESCRIBE statement, and it may optionally be used by the PREPARE,
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OPEN, CALL, FETCH, and EXECUTE statements. An SQLDA can be used in a DESCRIBE
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or PREPARE statement, altered with the addresses of storage areas<sup class="fn"><a id="wq1971" name="wq1971" href="rbafzmstsqldda.htm#wq1972">102</a></sup>, and then used again in a FETCH statement.</p>
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<p>SQLDAs are supported for all languages, but predefined declarations are
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provided only for C (and C++), COBOL, ILE RPG, PL/I, and REXX. In REXX, the
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SQLDA is somewhat different than in the other languages; for information on
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the use of SQLDAs in REXX, see the <a href="../rzajp/rzajpkickoff.htm">Embedded SQL Programming</a> book.</p>
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<p>The meaning of the information in an SQLDA depends on its use.</p>
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<ul>
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<li><span>When an SQLDA is used in a DESCRIBE or PREPARE statement,</span> an
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SQLDA provides information to an application program about a prepared <var class="pv">select-statement</var>. <a id="idx3438" name="idx3438"></a><a id="idx3439" name="idx3439"></a> Each column of the
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result table is described in an SQLVAR occurrence or set of related SQLVAR
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occurrences.</li>
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<li>In OPEN, EXECUTE, CALL, and FETCH, an SQLDA provides information to the
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database manager about storage areas for input or output data. Each storage
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area is described in the SQLVARs.
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<ul>
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<li>For OPEN and EXECUTE of a statement other than CALL, each SQLVAR occurrence
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or set of related SQLVAR occurrences describes a storage area that is used
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to contain an input value which is substituted for a parameter marker in the
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associated SQL statement that was previously prepared.</li>
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<li>For FETCH, each SQLVAR occurrence or set of related SQLVAR occurrences
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describes a <span>storage area</span> that is used to contain an output value
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from a row of the result table.</li>
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<li>For CALL and EXECUTE of a prepared CALL statement, each SQLVAR occurrence
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or set of related SQLVAR occurrences describes a <span>storage area</span> that
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is used to contain an input or output value (or both) that corresponds to
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an argument in the argument list for the procedure.</li></ul></li></ul>
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<p>An SQLDA consists of four variables in a header followed by an arbitrary
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number of occurrences of a <var class="pv">base SQLVAR</var>. When the SQLDA desribes either
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LOBs or distint types the base SQLVARs are followed by the same number of
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occurrences of an <var class="pv">extended SQLVAR</var>.</p>
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<dl>
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<dt class="bold">Base SQLVAR entry </dt>
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<dd>The base SQLVAR entry is always present. The fields of this entry contain
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the base information about the column or variable such as data type code,
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length attribute (except for LOBs), column name (or label), CCSID, variable
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address, and indicator variable address.
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</dd>
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<dt class="bold">Extended SQLVAR entry </dt>
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<dd>The extended SQLVAR entry is needed (for each column) if the result
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includes any LOB or distinct type columns. For distinct types, the extended
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SQLVAR contains the distinct type name. For LOBs, the extended SQLVAR contains
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the length attribute of the variable and a pointer to the buffer that contains
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the actual length. If locators or file reference variables are used to represent
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LOBs, an extended SQLVAR is not necessary.
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<p>The extended SQLVAR entry is
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also needed for each column when:</p>
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<ul>
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<li>USING BOTH is specified, which indicates that column names and labels
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are returned.</li>
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<li>USING ALL is specified, which indicates that column names, labels, and
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system column names are returned.</li></ul>
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<p>The fields in the extended SQLVAR that return LOB and distinct
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type information do not overlap, and the fields that return LOB and label
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information do not overlap. Depending on the combination of labels, LOBs and
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distinct types, more than one extended SQLVAR entry per column may be required
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to return the information. See <a href="rbafzmstfielddescsqlda.htm#howmany">Determining how many SQLVAR occurrences are needed</a>.</p>
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</dd>
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</dl>
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<hr /><div class="fnnum"><a id="wq1972" name="wq1972" href="rbafzmstsqldda.htm#wq1971">102</a>.</div>
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<div class="fntext">A storage
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area could be the storage for a variable defined in the program (that may
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also be a host variable) or an area of storage explicitly allocated by the
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application.</div>
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<br />
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<hr /><br />
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[ <a href="#Top_Of_Page">Top of Page</a> | <a href="rbafzmstincludesqlca.htm">Previous Page</a> | <a href="rbafzmstfielddescsqlda.htm">Next Page</a> | <a href="rbafzmst02.htm#wq1">Contents</a> |
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<a href="rbafzmstindex.htm#index">Index</a> ]
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<a id="Bot_Of_Page" name="Bot_Of_Page"></a>
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</body>
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</html>
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