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142 lines
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<title>Define complex search conditions</title>
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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">Define complex search conditions</h1>
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<div><p>In addition to the basic comparison predicates (=, >, <,
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and so on), a search condition can contain any of the predicates BETWEEN,
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IN, EXISTS, IS NULL, and LIKE. </p>
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<div class="section"><p>A search condition can include a scalar fullselect. </p>
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</div>
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<div class="section"><p>For character, or UCS-2 or UTF-16 graphic column predicates, the
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sort sequence is applied to the operands before evaluation of the predicates
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for BETWEEN, IN, EXISTS, and LIKE clauses. </p>
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</div>
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<div class="section"><p>You can also perform multiple search conditions.</p>
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<ul><li><strong>BETWEEN ... AND ...</strong> is used to specify a search condition that
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is satisfied by any value that falls on or between two other values. For example,
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to find all employees who were hired in 1987, you can use this: <pre>… <strong> WHERE</strong> HIREDATE <strong>BETWEEN</strong> '1987-01-01' <strong>AND</strong> '1987-12-31'</pre>
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<p>The BETWEEN keyword is inclusive. A more complex, but explicit, search
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condition that produces the same result is: </p>
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<pre>… <strong>WHERE</strong> HIREDATE >= '1987-01-01' <strong>AND</strong> HIREDATE <= '1987-12-31'</pre>
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</li>
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<li><strong>IN</strong> says you are interested in rows in which the value of the specified
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expression is among the values you listed. For example, to find the names
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of all employees in departments A00, C01, and E21, you can specify: <pre>… <strong>WHERE</strong> WORKDEPT <strong>IN</strong> ('A00', 'C01', 'E21')</pre>
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</li>
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<li><strong>EXISTS</strong> says you are interested in testing for the existence of
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certain rows. For example, to find out if there are any employees that have
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a salary greater than 60000, you can specify: <pre><strong>EXISTS (SELECT * FROM</strong> EMPLOYEE <strong>WHERE</strong> SALARY > 60000)</pre>
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</li>
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<li><strong>IS NULL</strong> says that you are interested in testing for null values.
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For example, to find out if there are any employees without a phone listing,
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you can specify: <pre>… <strong>WHERE</strong> EMPLOYEE.PHONE <strong>IS NULL</strong></pre>
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</li>
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<li><strong>LIKE</strong> says you are interested in rows in which an expression is
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similar to the value you supply. When you use LIKE, SQL searches for a character
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string similar to the one you specify. The degree of similarity is determined
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by two special characters used in the string that you include in the search
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condition: <dl><dt class="dlterm">_</dt>
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<dd>An underline character stands for any single character.</dd>
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<dt class="dlterm">%</dt>
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<dd>A percent sign stands for an unknown string of 0 or more characters. If
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the percent sign starts the search string, then SQL allows 0 or more character(s)
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to precede the matching value in the column. Otherwise, the search string
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must begin in the first position of the column.</dd>
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</dl>
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<div class="note"><span class="notetitle">Note:</span> If you are operating on MIXED data, the following distinction
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applies: an SBCS underline character refers to one SBCS character. No such
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restriction applies to the percent sign; that is, a percent sign refers to
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any number of SBCS or DBCS characters. See <a href="../db2/rbafzmst02.htm">SQL Reference</a> in the <span class="keyword">iSeries™ Information Center</span> for
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more information about the LIKE predicate and MIXED data.</div>
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<p>Use the
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underline character or percent sign either when you do not know or do not
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care about all the characters of the column's value. For example, to find
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out which employees live in Minneapolis, you can specify: </p>
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<pre>… <strong>WHERE</strong> ADDRESS <strong>LIKE</strong> '%MINNEAPOLIS%'</pre>
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<p>SQL
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returns any row with the string MINNEAPOLIS in the ADDRESS column, no matter
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where the string occurs.</p>
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<p>In another example, to list the towns whose
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names begin with 'SAN', you can specify: </p>
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<pre>… <strong>WHERE</strong> TOWN <strong>LIKE</strong> 'SAN%'</pre>
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<p>If
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you want to find any addresses where the street name isn't in your master
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street name list, you can use an expression in the LIKE expression. In this
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example, the STREET column in the table is assumed to be upper case. </p>
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<pre>… <strong>WHERE UCASE</strong> (:address_variable) <strong>NOT LIKE</strong> '%'||STREET||'%'</pre>
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<p>If you want to search for a character string that contains either the
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underscore or percent character, use the ESCAPE clause to specify an escape
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character. For example, to see all businesses that have a percent in their
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name, you can specify:</p>
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<pre>… <strong>WHERE</strong> BUSINESS_NAME <strong>LIKE</strong> '%@%%' ESCAPE '@'</pre>
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The
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first and last percent characters in the LIKE string are interpreted as the
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normal LIKE percent characters. The combination '@%' is taken
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as the actual percent character.</li>
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</ul>
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</div>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="rbafyspeciallike.htm">Special considerations for LIKE</a></strong><br />
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Here are some special considerations for using LIKE.</li>
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<li class="ulchildlink"><strong><a href="rbafymultiplewhere.htm">Multiple search conditions within a WHERE clause</a></strong><br />
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You can qualify your request further by coding a search condition that includes several predicates.</li>
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</ul>
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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="rbafysubquery.htm" title="You can use subqueries in a search condition as another way to select your data. Subqueries can be used anywhere an expression can be used.">Use subqueries</a></div>
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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="rbafywhere.htm" title="The WHERE clause specifies a search condition that identifies the row or rows you want to retrieve, update, or delete.">Specify a search condition using the WHERE clause</a></div>
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<div><a href="rbafywhereexp.htm" title="An expression in a WHERE clause names or specifies something you want to compare to something else.">Expressions in the WHERE clause</a></div>
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<div><a href="rbafymultiplewhere.htm" title="You can qualify your request further by coding a search condition that includes several predicates.">Multiple search conditions within a WHERE clause</a></div>
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<div><a href="rbafyspeciallike.htm" title="Here are some special considerations for using LIKE.">Special considerations for LIKE</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="../db2/rbafzmstch2pred.htm">Predicates</a></div>
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</div>
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</div>
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</body>
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