109 lines
6.1 KiB
HTML
109 lines
6.1 KiB
HTML
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<meta name="DC.Title" content="Example 1: Define fields derived from existing field definitions" />
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<meta name="abstract" content="This example shows the use of derived fields." />
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<title>Example 1: Define fields derived from existing field definitions</title>
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</head>
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<body id="rbafofdefdex1"><a name="rbafofdefdex1"><!-- --></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">Example 1: Define fields derived from existing field definitions</h1>
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<div><p>This example shows the use of derived fields.</p>
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<div class="section"><p>Assume that you have the <em>Price</em> and <em>Qty</em> fields in
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the record format. You can multiply one field by the other by using the Open
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Query File (OPNQRYF) command to create the derived <em>Exten</em> field. You
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want FILEA to be processed, and you have already created FILEAA. Assume that
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the record formats for the files contain the following fields:</p>
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</div>
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<table cellpadding="4" cellspacing="0" border="1" class="tableborder"><tr><td>
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<table cellpadding="4" cellspacing="0" summary="" width="100%" border="0"><thead align="left"><tr><th align="left" valign="bottom" width="50%" id="d0e30">FILEA</th>
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<th align="left" valign="bottom" width="50%" id="d0e32">FILEAA</th>
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</tr>
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</thead>
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<tbody><tr><td align="left" valign="top" width="50%" headers="d0e30 ">Order</td>
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<td align="left" valign="top" width="50%" headers="d0e32 ">Order</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e30 ">Item</td>
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<td align="left" valign="top" width="50%" headers="d0e32 ">Item</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e30 ">Qty</td>
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<td align="left" valign="top" width="50%" headers="d0e32 ">Exten</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e30 ">Price</td>
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<td align="left" valign="top" width="50%" headers="d0e32 ">Brfdsc</td>
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</tr>
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<tr><td align="left" valign="top" width="50%" headers="d0e30 ">Descrp</td>
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<td valign="top" width="50%" headers="d0e32 "> </td>
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</tr>
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</tbody>
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</table>
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</td></tr></table>
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<div class="section"><p>The <em>Exten</em> field is a mapped field. Its value is determined
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by multiplying <em>Qty</em> times <em>Price</em>. It is not necessary to have
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either the <em>Qty</em> or <em>Price</em> field in the new format, but they can
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exist in that format, too, if you want. The <em>Brfdsc</em> field is a brief
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description of the <em>Descrp</em> field (it uses the first 10 characters).</p>
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</div>
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<div class="section"><div class="p">Assume that you have specified PGMF to process the
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new format. To create this program, use FILEAA as the file to read. You can
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specify: <pre>OVRDBF FILE(FILEAA) TOFILE(FILEA) SHARE(*YES)
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OPNQRYF FILE(FILEA) FORMAT(FILEAA) +
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MAPFLD((EXTEN 'PRICE * QTY') +
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(BRFDSC 'DESCRP'))
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CALL PGM(PGMF) /* Created using file FILEAA as input */
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CLOF OPNID(FILEA)
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DLTOVR FILE(FILEAA)</pre>
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</div>
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</div>
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<div class="section"><p>Notice that the attributes of the <em>Exten</em> field are those
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defined in the record format for FILEAA. If the value calculated for the field
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is too large, an exception is sent to the program.</p>
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</div>
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<div class="section"><p>It is not necessary to use the substring function to map to the <em>Brfdsc</em> field
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if you only want the characters from the beginning of the field. The length
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of the <em>Brfdsc</em> field is defined in the FILEAA record format.</p>
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</div>
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<div class="section"><div class="p">All fields in the format specified on the FORMAT parameter must
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be described on the OPNQRYF command. That is, all fields in the output format
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must either exist in one of the record formats for the files specified on
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the FILE parameter or be defined on the MAPFLD parameter. If you have fields
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in the format on the FORMAT parameter that your program does not use, you
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can use the MAPFLD parameter to place zeros or blanks in the fields. Assume
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the <em>Fldc</em> field is a character field and the <em>Fldn</em> field is a
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numeric field in the output format, and you are using neither value in your
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program. You can avoid an error on the OPNQRYF command by specifying: <pre>MAPFLD((FLDC ' " " ')(FLDN 0))</pre>
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</div>
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</div>
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<div class="section"><p>Notice quotation marks enclose a blank value. By using a constant
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for the definition of an unused field, you avoid having to create a unique
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format for each use of the OPNQRYF command.</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="rbafofdefd.htm" title="Listed here are the operations allowed by defining fields derived from existing field definitions.">Define fields derived from existing field definitions</a></div>
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</div>
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</div>
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</body>
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</html> |