177 lines
9.8 KiB
HTML
177 lines
9.8 KiB
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<meta name="DC.Title" content="JOIN (Join) keyword—join logical files only" />
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<meta name="abstract" content="Use this join-level keyword to identify which pair of files are joined by the join specification in which you specify this keyword." />
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<meta name="description" content="Use this join-level keyword to identify which pair of files are joined by the join specification in which you specify this keyword." />
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<title>Physical and Logical Files, JOIN</title>
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<body id="lgjoin"><a name="lgjoin"><!-- --></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">JOIN (Join) keyword—join logical files only</h1>
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<div><p>Use this join-level keyword to identify which pair of files are
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joined by the join specification in which you specify this keyword.</p>
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<div class="section"><div class="p">The format of the keyword is: <pre>JOIN(from-file to-file)</pre>
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</div>
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<p>This
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keyword is valid only for join logical files.</p>
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<p>You can use file names
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or relative file numbers to indicate which files are to be joined. You must
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specify a relative file number if the same file is specified more than once
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on the JFILE keyword.</p>
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<p>If you specify file names, you must select files
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that you have specified only once on the JFILE keyword. On each JFILE keyword,
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the <em>from</em> file must occur before the <em>to</em> file.</p>
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<div class="p">If you specify
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numbers, they correspond to the files specified on the JFILE keyword. The
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following values are valid: <dl><dt><strong>File</strong></dt>
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<dd><strong>Valid values</strong></dd>
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<dt class="dlterm">From-file number</dt>
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<dd>1 through 255</dd>
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<dt class="dlterm">To-file number</dt>
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<dd>2 through 256</dd>
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</dl>
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</div>
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<p>The <em>from-file</em> number must always be less than
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the <em>to-file</em> number.</p>
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<p>Special rules apply to the order in which
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you specify <em>from</em> and <em>to</em> files. See example 3 in this topic for
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details.</p>
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<p>In a join logical file, each secondary file can be a <em>to</em> file
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only once.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">Join specifications for physical and logical files</h4><div class="p">To describe a join specification, follow the instructions:
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<ol><li>Specify J in position 17 immediately after the record level (before the
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first field name in positions 19 through 28). J in position 17 indicates
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the beginning of a join specification.</li>
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<li>Specify the JOIN keyword. The JOIN keyword is optional when only two
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files are specified on the JFILE keyword. When more than two physical files
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are specified on the JFILE keyword, one JOIN keyword is required for each
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secondary file.</li>
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<li>Specify the JFLD keyword at least once for each join specification.</li>
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<li>The end of the join specification is indicated by another J in position
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17 or by a field name specified in positions 19 through 28.</li>
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</ol>
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</div>
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<p>There must be one join specification for each secondary file specified
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on the JFILE keyword. Therefore, at least one join specification is required
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in a join logical file.</p>
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<p>You can specify the JOIN keyword only once within
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a join specification.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">Examples</h4><p>The following examples show how to specify
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the JOIN keyword.</p>
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</div>
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<div class="example"><h4 class="sectiontitle">Example 1</h4><pre>|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
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00010A R RECORD1 JFILE(PFA PFB PFC)
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00020A J JOIN(PFA PFB)
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00030A JFLD(NAME1 NAME2)
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00040A J JOIN(PFA PFC)
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00050A JFLD(NAME1 NAME3)
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00060A NAME1
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A</pre>
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<p>In this example, PFA is joined to PFB and also to PFC.</p>
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</div>
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<div class="example"><h4 class="sectiontitle">Example 2</h4><p>The following example shows how to specify
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JOIN using relative file numbers.</p>
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<pre>|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
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00010A R RECORD1 JFILE(PFA PFB PFC)
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00020A J JOIN(1 2)
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00030A JFLD(NAME1 NAME2)
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00040A J JOIN(1 3)
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00050A JFLD(NAME1 NAME3)
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00060A NAME1
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A</pre>
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<p>Example 2 is equivalent to example
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1. PFA is the first physical file specified on the JFILE keyword and has relative
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file number 1. PFB and PFC are the second and third files specified on the
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JFILE keyword. PFB has relative file number 2, and PFC relative file number
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3.</p>
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</div>
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<div class="example"><h4 class="sectiontitle">Example 3</h4><p>The following example shows the order
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of associated physical files.</p>
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<pre>|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
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00010A R J3 JFILE(VENDORS PARTS PARTWARE +
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00020A WAREHOUSE
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<span><span>1</span></span>
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00030A J JOIN(<strong>1</strong> <strong>2</strong>) <span><span>2</span></span>
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00040A JFLD(VNBR VNUM)
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00050A J JOIN(<strong>2</strong> <strong>3</strong>) <span><span>3</span></span>
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00060A JFLD(PNBR PNBR)
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00070A J JOIN(<strong>3</strong> <strong>4</strong>) <span><span>3</span></span>
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00080A JFLD(WNBR WNBR)
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00090A VNAME
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00100A VAD1
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00110A VAD2
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00120A PNBR JREF(2)
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00130A WNBR JREF(4)
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00140A BIN
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00150A QOH
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A</pre>
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<p>The join logical file in this example
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is based on four physical files. The VENDORS file, which is specified first
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on the JFILE keyword, is the primary file and has relative file number 1.
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The PARTS, PARTWARE, and WAREHOUSE files are secondary files. PARTS has relative
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file number 2, PARTWARE relative file number 3, and WAREHOUSE relative file
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number 4.</p>
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<div class="p">Notice the pattern of numbers specified on the JOIN keywords:
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<dl><dt class="dlterm"><span>1</span></dt>
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<dd>The first parameter value on the first JOIN keyword (the first <em>from</em> file)
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must be the primary file.</dd>
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<dt class="dlterm"><span>2</span></dt>
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<dd>The second parameter values specified on the JOIN keywords
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(<em>to</em> files) must reflect the same order as the secondary files on the
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JFILE keyword. If file names are specified instead of relative file numbers,
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they should be specified in the following order: <pre>J JOIN(VENDORS PARTS)
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J JOIN(PARTS PARTWARE)
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J JOIN(PARTWARE WAREHOUSE)</pre>
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</dd>
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<dt class="dlterm"><span>3</span></dt>
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<dd>On each JOIN keyword, the <em>from</em> and <em>to</em> files must be specified
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in ascending order.</dd>
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</dl>
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<div class="note"><span class="notetitle">Note:</span> A file can be specified as a <em>from</em> file more than
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once. For example, the parameters on the JOIN keywords before might
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be specified as follows: <pre>J JOIN(1 2)
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J JOIN(2 3)
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J JOIN(2 4)</pre>
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</div>
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</div>
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<p>However, a file can be specified as
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a <em>to</em> file only once.</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="rzakbmstlfkeyw.htm" title="This topic lists valid keyword entries for describing physical and logical files. They are typed in positions 45 through 80 (functions).">Keyword entries for physical and logical files (positions 45 through 80)</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="lftype.htm" title="Type a value in this position to identify the type of name or, for logical files, the type of specification. If you specify a name type, the name is specified in positions 19 through 28.">Type of name or specification for physical and logical files (position 17)</a></div>
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<div><a href="rzakbmstljfile.htm" title="Use this record-level keyword to identify the physical files containing the data to be accessed through the join logical file you are defining.">JFILE (Joined Files) keyword—join logical files only</a></div>
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</div>
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</div>
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