103 lines
6.3 KiB
HTML
103 lines
6.3 KiB
HTML
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<title>Example: Describe a logical file using DDS</title>
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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">Example: Describe a logical file using DDS</h1>
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<div><p>This example shows how to describe a logical file using DDS.</p>
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<div class="section"><div class="p">The DDS for a logical file, shown in the next example, must be
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in the following order: <dl><dt class="dlterm">1</dt>
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<dd>File-level entries (optional). In this example, the UNIQUE
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keyword indicates that for this file the key value for each record must be
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unique; no duplicate key values are allowed.</dd>
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</dl>
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</div>
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</div>
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<div class="section"><div class="p">For each record format: <dl><dt class="dlterm">2</dt>
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<dd>Record format level entries. In this example, the record format name,
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the associated physical file, and an optional text description are specified.</dd>
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<dt class="dlterm">3</dt>
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<dd>Field-level entries (optional). In this example, each field name used
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in the record format is specified.</dd>
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<dt class="dlterm">4</dt>
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<dd>Key field level entries (optional). In this example, the <em>Order</em> field
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is used as a key field.</dd>
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<dt class="dlterm">5</dt>
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<dd>Select/omit field level entries (optional). In this example, all records
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whose <em>Opnsts</em> field contains a value of N are omitted from the file's
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access path. That is, programs reading records from this file will never see
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a record whose <em>OPNSTS</em> field contains an N value.</dd>
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<dt class="dlterm">6</dt>
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<dd>Comment.</dd>
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</dl>
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</div>
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</div>
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<div class="example"> <pre>|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
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A* ORDER HEADER FILE (ORDHDRP)
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A <strong>6</strong>
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A <strong>1</strong> UNIQUE
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A <strong>2</strong> R ORDHDR PFILE(ORDHDRP)
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A <strong>3</strong> ORDER TEXT('Order number')
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A CUST TEXT('Customer number')
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A .
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A .
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A .
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A <strong>4</strong> K ORDER
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A O OPNSTS <strong>5</strong> CMP(EQ 'N')
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A S ALL</pre>
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</div>
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<div class="section"><p>A
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logical file must be created after all physical files on which it is based
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are created. The PFILE keyword in the previous example is used to specify
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the physical file or files on which the logical file is based.</p>
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</div>
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<div class="section"><div class="p">Record formats in a logical file can be: <ul><li>A new record format based on fields from a physical file</li>
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<li>The same record format as in a previously described physical or logical
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file.</li>
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</ul>
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</div>
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</div>
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<div class="section"><p>Fields in the logical file record format must either appear in
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the record format of at least one of the physical files or be derived from
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the fields of the physical files on which the logical file is based.</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="rbafodescdds.htm" title="When you describe a database file using data description specifications (DDS), you can describe information at the file, record-format, join, field, key, and select/omit levels.">Describe database files using DDS</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="rbafosharf.htm" title="A record format can be described once in either a physical or a logical file (except a join logical file) and can be used by many files. When you describe a new file, you can specify that the record format of an existing file is to be used by the new file.">Share existing record format descriptions in a database file</a></div>
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<div><a href="rbafologif.htm" title="These topics discuss some of the unique considerations for creating logical files.">Set up logical files</a></div>
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</div>
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</div>
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</body>
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