113 lines
6.6 KiB
HTML
113 lines
6.6 KiB
HTML
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<meta name="DC.Title" content="HAVING clause" />
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<meta name="abstract" content="The HAVING clause specifies a search condition for the groups selected by GROUP BY clause." />
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<meta name="DC.subject" content="SELECT statement, HAVING, example, clause" />
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<title>HAVING clause</title>
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</head>
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<body id="rbafyhaving"><a name="rbafyhaving"><!-- --></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">HAVING clause</h1>
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<div><p>The HAVING clause specifies a search condition for the groups selected
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by GROUP BY clause.</p>
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<div class="section"><p>The HAVING clause says that you want <em>only</em> those groups
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that satisfy the condition in that clause. Therefore, the search condition
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you specify in the HAVING clause must test properties of each group rather
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than properties of individual rows in the group.</p>
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</div>
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<div class="section"><p>The HAVING clause follows the GROUP BY clause and can contain
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the same kind of search condition you can specify in a WHERE clause. In addition,
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you can specify aggregate functions in a HAVING clause. For example, suppose
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you wanted to retrieve the average salary of women in each department. To
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do this, use the AVG aggregate function and group the resulting rows by WORKDEPT
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and specify a WHERE clause of SEX = <samp class="codeph">'</samp>F<samp class="codeph">'</samp>.</p>
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</div>
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<div class="section"><p>To specify that you want this data only when all the female employees
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in the selected department have an education level equal to or greater than
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16 (a college graduate), use the HAVING clause. The HAVING clause tests a
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property of the group. In this case, the test is on MIN(EDLEVEL), which is
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a group property:</p>
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</div>
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<div class="section"><pre><strong>SELECT</strong> WORKDEPT, <strong>DECIMAL</strong>(<strong>AVG</strong>(SALARY),5,0) <strong>AS</strong> AVG_WAGES, <strong>MIN</strong>(EDLEVEL) <strong>AS</strong> MIN_EDUC
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<strong>FROM</strong> CORPDATA.EMPLOYEE
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<strong>WHERE</strong> SEX='F'
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<strong>GROUP BY</strong> WORKDEPT
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<strong>HAVING MIN</strong>(EDLEVEL)>=16</pre>
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<p>Results in:</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="hsides" border="1" rules="all"><thead align="left"><tr><th valign="top" id="d0e91">WORKDEPT</th>
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<th valign="top" id="d0e93">AVG_WAGES</th>
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<th valign="top" id="d0e95">MIN_EDUC</th>
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</tr>
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</thead>
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<tbody><tr><td valign="top" headers="d0e91 ">A00</td>
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<td valign="top" headers="d0e93 ">49625</td>
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<td valign="top" headers="d0e95 ">18</td>
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</tr>
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<tr><td valign="top" headers="d0e91 ">C01</td>
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<td valign="top" headers="d0e93 ">29722</td>
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<td valign="top" headers="d0e95 ">16</td>
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</tr>
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<tr><td valign="top" headers="d0e91 ">D11</td>
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<td valign="top" headers="d0e93 ">25817</td>
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<td valign="top" headers="d0e95 ">17</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"><div class="p">You can use multiple predicates in a HAVING clause by connecting
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them with AND and OR, and you can use NOT for any predicate of a search condition.
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<div class="note"><span class="notetitle">Note:</span> If you intend to update a column or delete a row, you cannot include
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a GROUP BY or HAVING clause in the SELECT statement within a DECLARE CURSOR
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statement. These clauses make it a read-only cursor. </div>
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</div>
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</div>
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<div class="section"><p>Predicates with arguments that are not aggregate
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functions can be coded in either WHERE or HAVING clauses. It is typically
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more efficient to code the selection criteria in the WHERE clause because
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it is handled earlier in the query processing. The HAVING selection is performed
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in post processing of the result table.</p>
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</div>
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<div class="section"><p>If the search condition contains predicates involving character,
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or UCS-2 or UTF-16 graphic columns, the sort sequence in effect when the query
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is run is applied to those predicates. </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="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 class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="rbafyussisql.htm" title="A sort sequence defines how characters in a character set relate to each other when they are compared or ordered. Normalization allows you to compare strings that contain combining characters.">Sort sequences and normalization in SQL</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="rbafycurs.htm" title="When SQL runs a select statement, the resulting rows comprise the result table. A cursor provides a way to access a result table.">Use a cursor</a></div>
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</div>
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</div>
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</body>
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