343 lines
17 KiB
HTML
343 lines
17 KiB
HTML
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<meta name="abstract" content="Online analytical processing (OLAP) specifications are used to return ranking numbers and row numbers for the result rows of a query. You can specify RANK, DENSE_RANK, and ROW_NUMBER." />
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<title>Use OLAP specifications</title>
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<body id="rbafyolap"><a name="rbafyolap"><!-- --></a>
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<img src="./delta.gif" alt="Start of change" /><!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Use OLAP specifications</h1>
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<div><p><span>Online analytical processing (OLAP) specifications
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are used to return ranking numbers and row numbers for the result rows of
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a query. You can specify RANK, DENSE_RANK, and ROW_NUMBER.</span></p>
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<div class="section"><h4 class="sectiontitle">Example: Ranking and row numbering</h4><div class="p">Suppose you want
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a list of the top 10 salaries along with their ranking. The following query
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generates the ranking number for you.<pre> <strong>SELECT</strong> EMPNO, SALARY
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<strong>RANK()</strong> <strong>OVER</strong>(<strong>ORDER BY</strong> SALARY <strong>DESC</strong>),
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<strong>DENSE_RANK()</strong> <strong>OVER</strong>(<strong>ORDER BY</strong> SALARY <strong>DESC</strong>),
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<strong>ROW_NUMBER()</strong> <strong>OVER</strong>(<strong>ORDER BY</strong> SALARY <strong>DESC</strong>)
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<strong>FROM</strong> EMPLOYEE
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<strong>FETCH</strong> <strong>FIRST</strong> 10 <strong>ROWS</strong> <strong>ONLY</strong></pre>
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</div>
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<p>This
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query returns the following information.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><caption>Table 1. Results of the previous
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query</caption><thead align="left"><tr valign="bottom"><th valign="bottom" id="d0e86">EMPNO</th>
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<th valign="bottom" id="d0e88">SALARY</th>
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<th valign="bottom" id="d0e90">RANK</th>
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<th valign="bottom" id="d0e92">DENSE_RANK</th>
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<th valign="bottom" id="d0e94">ROW_NUMBER</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e86 ">000010</td>
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<td valign="top" headers="d0e88 ">52,750.00</td>
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<td valign="top" headers="d0e90 ">1</td>
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<td valign="top" headers="d0e92 ">1</td>
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<td valign="top" headers="d0e94 ">1</td>
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</tr>
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<tr><td valign="top" headers="d0e86 ">000110</td>
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<td valign="top" headers="d0e88 ">46,500.00</td>
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<td valign="top" headers="d0e90 ">2</td>
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<td valign="top" headers="d0e92 ">2</td>
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<td valign="top" headers="d0e94 ">2</td>
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</tr>
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<tr><td valign="top" headers="d0e86 ">200010</td>
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<td valign="top" headers="d0e88 ">46,500.00</td>
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<td valign="top" headers="d0e90 ">2</td>
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<td valign="top" headers="d0e92 ">2</td>
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<td valign="top" headers="d0e94 ">3</td>
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</tr>
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<tr><td valign="top" headers="d0e86 ">000020</td>
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<td valign="top" headers="d0e88 ">41,250.00</td>
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<td valign="top" headers="d0e90 ">4</td>
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<td valign="top" headers="d0e92 ">3</td>
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<td valign="top" headers="d0e94 ">4</td>
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</tr>
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<tr><td valign="top" headers="d0e86 ">000050 </td>
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<td valign="top" headers="d0e88 ">40,175.00</td>
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<td valign="top" headers="d0e90 ">5</td>
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<td valign="top" headers="d0e92 ">4</td>
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<td valign="top" headers="d0e94 ">5</td>
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</tr>
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<tr><td valign="top" headers="d0e86 ">000030</td>
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<td valign="top" headers="d0e88 ">38,250.00</td>
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<td valign="top" headers="d0e90 ">6</td>
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<td valign="top" headers="d0e92 ">5</td>
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<td valign="top" headers="d0e94 ">6</td>
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</tr>
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<tr><td valign="top" headers="d0e86 ">000070</td>
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<td valign="top" headers="d0e88 ">36,170.00</td>
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<td valign="top" headers="d0e90 ">7</td>
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<td valign="top" headers="d0e92 ">6</td>
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<td valign="top" headers="d0e94 ">7</td>
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</tr>
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<tr><td valign="top" headers="d0e86 ">000060</td>
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<td valign="top" headers="d0e88 ">32,250.00</td>
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<td valign="top" headers="d0e90 ">8</td>
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<td valign="top" headers="d0e92 ">7</td>
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<td valign="top" headers="d0e94 ">8</td>
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</tr>
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<tr><td valign="top" headers="d0e86 ">000220</td>
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<td valign="top" headers="d0e88 ">29,840.00</td>
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<td valign="top" headers="d0e90 ">9</td>
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<td valign="top" headers="d0e92 ">8</td>
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<td valign="top" headers="d0e94 ">9</td>
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</tr>
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<tr><td valign="top" headers="d0e86 ">200220</td>
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<td valign="top" headers="d0e88 ">29,840.00</td>
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<td valign="top" headers="d0e90 ">9</td>
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<td valign="top" headers="d0e92 ">8</td>
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<td valign="top" headers="d0e94 ">10</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>In this example, the SALARY descending order with the top 10 returned.
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The RANK column shows the relative ranking of each salary. Notice that there
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are two rows with the same salary at position 2. Each of those rows is assigned
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the same rank value. The following row is assigned the value of 4. RANK returns
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a value for a row that is one more than the total number of rows that precede
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that row. There are gaps in the numbering sequence whenever there are duplicates.</p>
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<p>In
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contrast, the DENSE_RANK column shows a value of 3 for the row directly after
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the duplicate rows. DENSE_RANK returns a value for a row that is one more
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than the number of distinct row values that precede it. There will never be
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gaps in the numbering sequence.</p>
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<p>ROW_NUMBER returns a unique number for
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each row. For rows that contain duplicate values according to the specified
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ordering, the assignment of a row number is arbitrary; the row numbers could
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be assigned in a different order for the duplicate rows when the query is
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run another time.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">Example: Ranking groups</h4><div class="p">In this example, suppose
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you want to find out which department has the highest average salary. The
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following query will group the data by department, determine the average salary
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for each department, and then rank the resulting averages.<pre><strong>SELECT</strong> WORKDEPT, <strong>INT</strong>(<strong>AVG</strong>(SALARY)) <strong>AS</strong> AVERAGE,
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<strong>RANK()</strong> <strong>OVER</strong>(<strong>ORDER BY</strong> <strong>AVG</strong>(SALARY) <strong>DESC</strong>) <strong>AS</strong> AVG_SALARY
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<strong>FROM</strong> EMPLOYEE
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<strong>GROUP BY</strong> WORKDEPT </pre>
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</div>
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<p>This query returns the following
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information.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><caption>Table 2. Results of previous query</caption><thead align="left"><tr valign="bottom"><th valign="bottom" id="d0e266">WORKDEPT</th>
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<th valign="bottom" id="d0e268">AVERAGE</th>
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<th valign="bottom" id="d0e270">AVG_SALARY</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e266 ">B01</td>
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<td valign="top" headers="d0e268 ">41,250</td>
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<td valign="top" headers="d0e270 ">1</td>
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</tr>
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<tr><td valign="top" headers="d0e266 ">A00</td>
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<td valign="top" headers="d0e268 ">40,850</td>
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<td valign="top" headers="d0e270 ">2</td>
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</tr>
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<tr><td valign="top" headers="d0e266 ">E01</td>
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<td valign="top" headers="d0e268 ">40,175</td>
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<td valign="top" headers="d0e270 ">3</td>
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</tr>
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<tr><td valign="top" headers="d0e266 ">C01</td>
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<td valign="top" headers="d0e268 ">29,722</td>
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<td valign="top" headers="d0e270 ">4</td>
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</tr>
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<tr><td valign="top" headers="d0e266 ">D21</td>
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<td valign="top" headers="d0e268 ">25,668</td>
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<td valign="top" headers="d0e270 ">5</td>
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</tr>
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<tr><td valign="top" headers="d0e266 ">D11</td>
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<td valign="top" headers="d0e268 ">25,147</td>
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<td valign="top" headers="d0e270 ">6</td>
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</tr>
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<tr><td valign="top" headers="d0e266 ">E21</td>
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<td valign="top" headers="d0e268 ">24,086</td>
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<td valign="top" headers="d0e270 ">7</td>
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</tr>
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<tr><td valign="top" headers="d0e266 ">E11</td>
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<td valign="top" headers="d0e268 ">21,020</td>
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<td valign="top" headers="d0e270 ">8</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 class="section"><h4 class="sectiontitle">Example: Ranking within a department</h4><div class="p">Suppose you
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want a list of employees along with how their bonus ranks within their department.
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Using the PARTITION BY clause, you can specify groups that are to be numbered
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separately.<pre><strong>SELECT</strong> LASTNAME, WORKDEPT, BONUS,
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<strong>DENSE_RANK()</strong> <strong>OVER</strong>(<strong>PARTITION BY</strong> WORKDEPT <strong>ORDER BY</strong> BONUS <strong>DESC</strong>)
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<strong>AS</strong> BONUS_RANK_IN_DEPT
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<strong>FROM</strong> EMPLOYEE
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<strong>WHERE</strong> WORKDEPT <strong>LIKE</strong> 'E%'</pre>
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</div>
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<p>This query returns
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the following information.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><caption>Table 3. Results of the previous query</caption><thead align="left"><tr valign="bottom"><th valign="bottom" width="25%" id="d0e377">LASTNAME</th>
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<th valign="bottom" width="25%" id="d0e379">WORKDEPT</th>
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<th valign="bottom" width="25%" id="d0e381">BONUS</th>
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<th valign="bottom" width="25%" id="d0e383">BONUS_RANK_in_DEPT</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" width="25%" headers="d0e377 ">GEYER</td>
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<td valign="top" width="25%" headers="d0e379 ">E01</td>
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<td valign="top" width="25%" headers="d0e381 ">800.00</td>
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<td valign="top" width="25%" headers="d0e383 ">1</td>
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</tr>
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<tr><td valign="top" width="25%" headers="d0e377 ">HENDERSON</td>
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<td valign="top" width="25%" headers="d0e379 ">E11</td>
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<td valign="top" width="25%" headers="d0e381 ">600.00</td>
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<td valign="top" width="25%" headers="d0e383 ">1</td>
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</tr>
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<tr><td valign="top" width="25%" headers="d0e377 ">SCHNEIDER</td>
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<td valign="top" width="25%" headers="d0e379 ">E11</td>
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<td valign="top" width="25%" headers="d0e381 ">500.00</td>
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<td valign="top" width="25%" headers="d0e383 ">2</td>
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</tr>
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<tr><td valign="top" width="25%" headers="d0e377 ">SCHWARTZ</td>
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<td valign="top" width="25%" headers="d0e379 ">E11</td>
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<td valign="top" width="25%" headers="d0e381 ">500.00</td>
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<td valign="top" width="25%" headers="d0e383 ">2</td>
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</tr>
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<tr><td valign="top" width="25%" headers="d0e377 ">SMITH</td>
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<td valign="top" width="25%" headers="d0e379 ">E11</td>
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<td valign="top" width="25%" headers="d0e381 ">400.00</td>
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<td valign="top" width="25%" headers="d0e383 ">3</td>
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</tr>
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<tr><td valign="top" width="25%" headers="d0e377 ">PARKER</td>
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<td valign="top" width="25%" headers="d0e379 ">E11</td>
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<td valign="top" width="25%" headers="d0e381 ">300.00</td>
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<td valign="top" width="25%" headers="d0e383 ">4</td>
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</tr>
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<tr><td valign="top" width="25%" headers="d0e377 ">SETRIGHT</td>
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<td valign="top" width="25%" headers="d0e379 ">E11</td>
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<td valign="top" width="25%" headers="d0e381 ">300.00</td>
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<td valign="top" width="25%" headers="d0e383 ">4</td>
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</tr>
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<tr><td valign="top" width="25%" headers="d0e377 ">SPRINGER</td>
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<td valign="top" width="25%" headers="d0e379 ">E11</td>
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<td valign="top" width="25%" headers="d0e381 ">300.00</td>
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<td valign="top" width="25%" headers="d0e383 ">4</td>
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</tr>
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<tr><td valign="top" width="25%" headers="d0e377 ">SPENSER</td>
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<td valign="top" width="25%" headers="d0e379 ">E21</td>
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<td valign="top" width="25%" headers="d0e381 ">500.00</td>
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<td valign="top" width="25%" headers="d0e383 ">1</td>
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</tr>
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<tr><td valign="top" width="25%" headers="d0e377 ">LEE</td>
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<td valign="top" width="25%" headers="d0e379 ">E21</td>
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<td valign="top" width="25%" headers="d0e381 ">500.00</td>
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<td valign="top" width="25%" headers="d0e383 ">1</td>
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</tr>
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<tr><td valign="top" width="25%" headers="d0e377 ">GOUNOT</td>
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<td valign="top" width="25%" headers="d0e379 ">E21</td>
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<td valign="top" width="25%" headers="d0e381 ">500.00</td>
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<td valign="top" width="25%" headers="d0e383 ">1</td>
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</tr>
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<tr><td valign="top" width="25%" headers="d0e377 ">WONG</td>
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<td valign="top" width="25%" headers="d0e379 ">E21</td>
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<td valign="top" width="25%" headers="d0e381 ">500.00</td>
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<td valign="top" width="25%" headers="d0e383 ">1</td>
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</tr>
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<tr><td valign="top" width="25%" headers="d0e377 ">ALONZO</td>
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<td valign="top" width="25%" headers="d0e379 ">E21</td>
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<td valign="top" width="25%" headers="d0e381 ">500.00</td>
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<td valign="top" width="25%" headers="d0e383 ">1</td>
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</tr>
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<tr><td valign="top" width="25%" headers="d0e377 ">MENTA</td>
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<td valign="top" width="25%" headers="d0e379 ">E21</td>
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<td valign="top" width="25%" headers="d0e381 ">400.00</td>
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<td valign="top" width="25%" headers="d0e383 ">2</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 class="section"><h4 class="sectiontitle">Example: Ranking and ordering by table expression results</h4><p>Suppose
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you want to find the top five employees whose salaries are the highest along
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with their department names. The department name is in the <em>department</em> table,
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so a join is needed. Since ordering is already being done in the nested table
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expression, that ordering can also be used for determining the ROW_NUMBER
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value. The ORDER BY ORDER OF <em>table</em> clause is used to do this.</p>
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<pre><strong>SELECT</strong> <strong>ROW_NUMBER()</strong> <strong>OVER</strong>(<strong>ORDER BY ORDER OF</strong> EMP),
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EMPNO, SALARY, DEPTNO, DEPTNAME
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<strong>FROM</strong> (<strong>SELECT</strong> EMPNO, WORKDEPT, SALARY
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<strong>FROM</strong> EMPLOYEE
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<strong>ORDER BY</strong> SALARY <strong>DESC</strong>
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<strong>FETCH</strong> <strong>FIRST</strong> 5 <strong>ROWS</strong> <strong>ONLY</strong>) EMP,
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DEPARTMENT
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<strong>WHERE</strong> DEPTNO = WORKDEPT</pre>
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<p>This query returns
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the following information.</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><caption>Table 4. Results of the previous query</caption><thead align="left"><tr valign="bottom"><th valign="bottom" width="20%" id="d0e579">ROW_NUMBER</th>
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<th valign="bottom" width="20%" id="d0e581">EMPNO</th>
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<th valign="bottom" width="20%" id="d0e583">SALARY</th>
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<th valign="bottom" width="20%" id="d0e585">DEPTNO</th>
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<th valign="bottom" width="20%" id="d0e587">DEPTNAME</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" width="20%" headers="d0e579 ">1</td>
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<td valign="top" width="20%" headers="d0e581 ">000010</td>
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<td valign="top" width="20%" headers="d0e583 ">52,750.00</td>
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<td valign="top" width="20%" headers="d0e585 ">A00</td>
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<td valign="top" width="20%" headers="d0e587 ">SPIFFY COMPUTER SERVICE DIV.</td>
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</tr>
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<tr><td valign="top" width="20%" headers="d0e579 ">2</td>
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<td valign="top" width="20%" headers="d0e581 ">000110</td>
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<td valign="top" width="20%" headers="d0e583 ">46,500.00</td>
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<td valign="top" width="20%" headers="d0e585 ">A00</td>
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<td valign="top" width="20%" headers="d0e587 ">SPIFFY COMPUTER SERVICE DIV.</td>
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</tr>
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<tr><td valign="top" width="20%" headers="d0e579 ">3</td>
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<td valign="top" width="20%" headers="d0e581 ">200010</td>
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<td valign="top" width="20%" headers="d0e583 ">46,500.00</td>
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<td valign="top" width="20%" headers="d0e585 ">A00</td>
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<td valign="top" width="20%" headers="d0e587 ">SPIFFY COMPUTER SERVICE DIV.</td>
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</tr>
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<tr><td valign="top" width="20%" headers="d0e579 ">4</td>
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<td valign="top" width="20%" headers="d0e581 ">000020</td>
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<td valign="top" width="20%" headers="d0e583 ">41,250.00</td>
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<td valign="top" width="20%" headers="d0e585 ">B01</td>
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<td valign="top" width="20%" headers="d0e587 ">PLANNING</td>
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</tr>
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<tr><td valign="top" width="20%" headers="d0e579 ">5</td>
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<td valign="top" width="20%" headers="d0e581 ">000050</td>
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<td valign="top" width="20%" headers="d0e583 ">40,175.00</td>
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<td valign="top" width="20%" headers="d0e585 ">E01</td>
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<td valign="top" width="20%" headers="d0e587 ">SUPPORT SERVICES</td>
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</tr>
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</tbody>
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</table>
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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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