186 lines
8.0 KiB
HTML
186 lines
8.0 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="Use INTERSECT keyword" />
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<meta name="abstract" content="The INTERSECT keyword returns a combined result set that consists of all of the rows existing in both result sets." />
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<meta name="description" content="The INTERSECT keyword returns a combined result set that consists of all of the rows existing in both result sets." />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Use INTERSECT keyword</title>
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</head>
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<body id="rbafyintersect"><a name="rbafyintersect"><!-- --></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">Use INTERSECT keyword</h1>
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<div><p>The INTERSECT keyword returns a combined result set that consists
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of all of the rows existing in both result sets.</p>
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<div class="section"><p>Suppose you want to find a list of employee numbers that includes:</p>
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<ul><li>People in department D11</li>
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<li>People whose assignments include projects MA2112, MA2113, and AD3111</li>
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</ul>
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<p>INTERSECT returns the all of the employee numbers that exist in both
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result sets. In other words, this query returns all of the people in department
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D11 who are also working on projects MA2112, MA2113, and AD3111.</p>
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</div>
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<div class="section"><p>To do this, specify:</p>
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<pre><strong>SELECT</strong> EMPNO
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<strong>FROM</strong> CORPDATA.EMPLOYEE
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<strong>WHERE</strong> WORKDEPT = 'D11'
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<strong>INTERSECT</strong>
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<strong>SELECT</strong> EMPNO
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<strong>FROM</strong> CORPDATA.EMPPROJACT
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<strong>WHERE</strong> PROJNO = 'MA2112' <strong>OR</strong>
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PROJNO = 'MA2113' <strong>OR</strong>
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PROJNO = 'AD3111'
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<strong>ORDER BY</strong> EMPNO</pre>
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</div>
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<div class="section"><p>To better understand the results from these SQL statements, imagine
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that SQL goes through the following process:</p>
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</div>
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<div class="section"><p>Step 1. SQL processes the first SELECT statement:</p>
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<pre><strong>SELECT</strong> EMPNO
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<strong>FROM</strong> CORPDATA.EMPLOYEE
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<strong>WHERE</strong> WORKDEPT = 'D11'</pre>
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<p>Which results in an interim
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result table:</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="hsides" border="1" rules="all"><thead align="left"><tr valign="top"><th valign="top" id="d0e84">EMPNO from CORPDATA.EMPLOYEE</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e84 ">000060</td>
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</tr>
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<tr><td valign="top" headers="d0e84 ">000150</td>
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</tr>
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<tr><td valign="top" headers="d0e84 ">000160</td>
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</tr>
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<tr><td valign="top" headers="d0e84 ">000170</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e84 ">000180</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e84 ">000190</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e84 ">000200</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e84 ">000210</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e84 ">000220</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e84 ">200170</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e84 ">200220</td>
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</tr>
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</tbody>
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</table>
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</div>
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<p>Step 2. SQL processes the second SELECT statement:</p>
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<pre><strong>SELECT</strong> EMPNO
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<strong>FROM</strong> CORPDATA.EMPPROJACT
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<strong>WHERE</strong> PROJNO='MA2112' <strong>OR</strong>
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PROJNO= 'MA2113' <strong>OR</strong>
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PROJNO= 'AD3111'</pre>
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<p>Which results in another interim
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result table:</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="hsides" border="1" rules="all"><thead align="left"><tr valign="top"><th valign="top" id="d0e145">EMPNO from CORPDATA.EMPPROJACT</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e145 ">000230</td>
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</tr>
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<tr><td valign="top" headers="d0e145 ">000230</td>
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</tr>
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<tr><td valign="top" headers="d0e145 ">000240</td>
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</tr>
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<tr><td valign="top" headers="d0e145 ">000230</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e145 ">000230</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e145 ">000240</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e145 ">000230</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e145 ">000150</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e145 ">000170</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e145 ">000190</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e145 ">000170</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e145 ">000190</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e145 ">000150</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e145 ">000160</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e145 ">000180</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e145 ">000170</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e145 ">000210</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e145 ">000210</td>
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</tr>
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</tbody>
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</table>
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</div>
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<p>Step 3. SQL takes the first interim result table, compares it to
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the second interim result table, and returns the rows that exist in both tables
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minus any duplicate rows, and orders the results.</p>
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<pre><strong>SELECT</strong> EMPNO
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<strong>FROM</strong> CORPDATA.EMPLOYEE
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<strong>WHERE</strong> WORKDEPT = 'D11'
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<strong>INTERSECT</strong>
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<strong>SELECT</strong> EMPNO
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<strong>FROM</strong> CORPDATA.EMPPROJACT
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<strong>WHERE</strong> PROJNO='MA2112' <strong>OR</strong>
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PROJNO= 'MA2113' <strong>OR</strong>
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PROJNO= 'AD3111'
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<strong>ORDER BY</strong> EMPNO</pre>
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<p>Which results in a combined result table
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with values in ascending sequence:</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="hsides" border="1" rules="all"><thead align="left"><tr valign="top"><th valign="top" id="d0e242">EMPNO</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e242 ">000150</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e242 ">000160</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e242 ">000170</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e242 ">000180</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e242 ">000190</td>
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</tr>
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<tr valign="top"><td valign="top" headers="d0e242 ">000210</td>
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</tr>
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</tbody>
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</table>
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</div>
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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="rbafytexas.htm" title="Learn a variety of ways of tailoring your query to gather data using the SELECT statement. One way to do this is to use the SELECT statement in a program to retrieve a specific row (for example, the row for an employee). Furthermore, you can use clauses to gather data in a specific way.">Retrieve data using the SELECT statement</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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