125 lines
7.6 KiB
HTML
125 lines
7.6 KiB
HTML
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta name="DC.Title" content="Broadcast join with DB2 Multisystem" />
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<meta name="abstract" content="In a broadcast join, all of the selected records of one file are sent or broadcast to all the nodes of the other file before the join is performed." />
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<meta name="description" content="In a broadcast join, all of the selected records of one file are sent or broadcast to all the nodes of the other file before the join is performed." />
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<meta name="DC.subject" content="query, broadcast join, join, broadcast, example, broadcast join query" />
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<title>Broadcast join with DB2 Multisystem</title>
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</head>
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<body id="broadcast"><a name="broadcast"><!-- --></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">Broadcast join with DB2<sup>®</sup> Multisystem</h1>
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<div><p>In a broadcast join, all of the selected records of one file are
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sent or broadcast to all the nodes of the other file before the join is performed.</p>
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<div class="section"><p>This is the join method that is used for all nonequijoin queries.
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This method is also used when the join criteria uses fields that have a data
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type of date, time, timestamp, or floating-point numeric.</p>
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<p>In the following
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example, the distributed query optimizer decides to broadcast EMPLOYEE, because
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applying the selection JOB = 'Manager' results in broadcasting a smaller set
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of records. The temporary file at each node in the node group contains all
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the selected records. (Records are duplicated at each node.)</p>
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<p>SQL statement:</p>
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<pre> SELECT DEPTNAME, FIRSTNME, LASTNAME
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FROM DEPARTMENT, EMPLOYEE
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WHERE DEPTNO <> WORKDEPT AND JOB = 'Manager'</pre>
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<p>OPNQRYF
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command:</p>
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<pre> OPNQRYF FILE((DEPARTMENT) (EMPLOYEE))
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FORMAT(JOINFMT)
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QRYSLT('JOB *EQ 'Manager')
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JFLD((DEPTNO WORKDEPT *NE))</pre>
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<p>The
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distributed query optimizer sends the following two selected records to each
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node:</p>
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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="" border="0"><caption>Table 1. Records that the distributed query optimizer
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sends to each node</caption><thead align="left"><tr><th align="center" valign="bottom" width="17.22222222222222%" id="d0e77">Old node</th>
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<th align="left" valign="bottom" width="18.51851851851852%" id="d0e79">New node</th>
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<th align="left" valign="bottom" width="19.814814814814817%" id="d0e81">FIRSTNME</th>
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<th align="left" valign="bottom" width="21.85185185185185%" id="d0e83">LASTNAME</th>
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<th align="center" valign="bottom" width="22.59259259259259%" id="d0e85">WORKDEPT</th>
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</tr>
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</thead>
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<tbody><tr><td align="center" valign="top" width="17.22222222222222%" headers="d0e77 ">SYSA</td>
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<td align="left" valign="top" width="18.51851851851852%" headers="d0e79 ">SYSA, SYSB, SYSC</td>
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<td align="left" valign="top" width="19.814814814814817%" headers="d0e81 ">Christine</td>
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<td align="left" valign="top" width="21.85185185185185%" headers="d0e83 ">Haas</td>
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<td align="center" valign="top" width="22.59259259259259%" headers="d0e85 ">A00</td>
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</tr>
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<tr><td align="center" valign="top" width="17.22222222222222%" headers="d0e77 ">SYSC</td>
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<td align="left" valign="top" width="18.51851851851852%" headers="d0e79 ">SYSA, SYSB, SYSC</td>
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<td align="left" valign="top" width="19.814814814814817%" headers="d0e81 ">Michael</td>
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<td align="left" valign="top" width="21.85185185185185%" headers="d0e83 ">Thompson</td>
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<td align="center" valign="top" width="22.59259259259259%" headers="d0e85 ">B00</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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<p>Records returned by this query:</p>
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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="" border="0"><caption>Table 2. Display
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of the query results</caption><thead align="left"><tr><th align="left" valign="bottom" width="33.33333333333333%" id="d0e121">DEPTNAME</th>
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<th align="left" valign="bottom" width="33.33333333333333%" id="d0e123">FIRSTNME</th>
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<th align="left" valign="bottom" width="33.33333333333333%" id="d0e125">LASTNAME</th>
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</tr>
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</thead>
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<tbody><tr><td align="left" valign="top" width="33.33333333333333%" headers="d0e121 ">Support services</td>
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<td align="left" valign="top" width="33.33333333333333%" headers="d0e123 ">Michael</td>
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<td align="left" valign="top" width="33.33333333333333%" headers="d0e125 ">Thompson</td>
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</tr>
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<tr><td align="left" valign="top" width="33.33333333333333%" headers="d0e121 ">Planning</td>
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<td align="left" valign="top" width="33.33333333333333%" headers="d0e123 ">Christine</td>
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<td align="left" valign="top" width="33.33333333333333%" headers="d0e125 ">Haas</td>
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</tr>
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<tr><td align="left" valign="top" width="33.33333333333333%" headers="d0e121 ">Planning</td>
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<td align="left" valign="top" width="33.33333333333333%" headers="d0e123 ">Michael</td>
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<td align="left" valign="top" width="33.33333333333333%" headers="d0e125 ">Thompson</td>
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</tr>
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<tr><td align="left" valign="top" width="33.33333333333333%" headers="d0e121 ">Accounting</td>
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<td align="left" valign="top" width="33.33333333333333%" headers="d0e123 ">Christine</td>
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<td align="left" valign="top" width="33.33333333333333%" headers="d0e125 ">Haas</td>
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</tr>
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<tr><td align="left" valign="top" width="33.33333333333333%" headers="d0e121 ">Programming</td>
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<td align="left" valign="top" width="33.33333333333333%" headers="d0e123 ">Christine</td>
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<td align="left" valign="top" width="33.33333333333333%" headers="d0e125 ">Haas</td>
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</tr>
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<tr><td align="left" valign="top" width="33.33333333333333%" headers="d0e121 ">Programming</td>
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<td align="left" valign="top" width="33.33333333333333%" headers="d0e123 ">Michael</td>
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<td align="left" valign="top" width="33.33333333333333%" headers="d0e125 ">Thompson</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>
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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="joins.htm" title="In addition to the performance considerations for nondistributed join queries, more performance considerations exist for queries involving distributed files.">Implementation and optimization of join operations with DB2 Multisystem</a></div>
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</div>
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</div>
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</body>
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</html>
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