forked from docs/doc-exports
Su, Xiaomeng
04d4597cf3
Reviewed-by: Pruthi, Vineet <vineet.pruthi@t-systems.com> Co-authored-by: Su, Xiaomeng <suxiaomeng1@huawei.com> Co-committed-by: Su, Xiaomeng <suxiaomeng1@huawei.com>
28 lines
4.9 KiB
HTML
28 lines
4.9 KiB
HTML
<a name="dli_08_0189"></a><a name="dli_08_0189"></a>
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<h1 class="topictitle1">CASE Query Statement</h1>
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<div id="body8662426"><div class="section" id="dli_08_0189__en-us_topic_0093946914_s4325184a0e9943d3a27de28100b88383"><h4 class="sectiontitle">Function</h4><p id="dli_08_0189__en-us_topic_0093946914_aff27e6373888448a9c1ca51b24517473">This statement is used to obtain the value of <strong id="dli_08_0189__en-us_topic_0093946914_en-us_topic_0047959934_en-us_topic_0039551545_b5249473992014">boolean_expression</strong> for each WHEN statement in a specified order. Then return the first <strong id="dli_08_0189__en-us_topic_0093946914_b1487300845174810">result_expression</strong> with the value <strong id="dli_08_0189__en-us_topic_0093946914_b1910926701174810">TRUE</strong> of <strong id="dli_08_0189__en-us_topic_0093946914_b751484269174810">boolean_expression</strong>.</p>
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<div class="section" id="dli_08_0189__en-us_topic_0093946914_s73ab30b704ae427780c73b24c8236e25"><h4 class="sectiontitle">Syntax</h4><div class="codecoloring" codetype="Sql" id="dli_08_0189__screen338755164714"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">CASE</span><span class="w"> </span><span class="k">WHEN</span><span class="w"> </span><span class="n">boolean_expression</span><span class="w"> </span><span class="k">THEN</span><span class="w"> </span><span class="n">result_expression</span><span class="w"> </span><span class="p">[...</span><span class="n">n</span><span class="p">]</span><span class="w"> </span><span class="p">[</span><span class="k">ELSE</span><span class="w"> </span><span class="n">else_result_expression</span><span class="p">]</span><span class="w"> </span><span class="k">END</span><span class="p">;</span>
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</pre></div></td></tr></table></div>
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<div class="section" id="dli_08_0189__en-us_topic_0093946914_s3f0115d625ce413b8b240d827e306c11"><h4 class="sectiontitle">Keyword</h4><p id="dli_08_0189__en-us_topic_0093946914_a1331bd21ad0e4d24b59a904171c001b1">boolean_expression: can include subquery. However, the return value of boolean_expression can only be of Boolean type.</p>
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<div class="section" id="dli_08_0189__en-us_topic_0093946914_se79d37f2ee5447698898f6899b13a227"><h4 class="sectiontitle">Precautions</h4><p id="dli_08_0189__en-us_topic_0093946914_a1b9f325f604649d8b39e3ced294fbba0">If there is no Boolean_expression with the TRUE value, else_result_expression will be returned when the ELSE clause is specified. If the ELSE clause is not specified, NULL will be returned.</p>
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<div class="section" id="dli_08_0189__en-us_topic_0093946914_sfd78e465b949432ab97a48315d604ad1"><h4 class="sectiontitle">Example</h4><p id="dli_08_0189__en-us_topic_0093946914_a03f21279ca3e4d00b73ee2cad426ab29">To query the student table and return the related results for the name and score fields: EXCELLENT if the score is higher than 90, GOOD if the score ranges from 80 to 90, and BAD if the score is lower than 80, run the following statement:</p>
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<div class="codecoloring" codetype="Sql" id="dli_08_0189__screen1732521144714"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">name</span><span class="p">,</span><span class="w"> </span><span class="k">CASE</span><span class="w"> </span><span class="k">WHEN</span><span class="w"> </span><span class="n">score</span><span class="w"> </span><span class="o">>=</span><span class="w"> </span><span class="mi">90</span><span class="w"> </span><span class="k">THEN</span><span class="w"> </span><span class="s1">'EXCELLENT'</span><span class="w"> </span><span class="k">WHEN</span><span class="w"> </span><span class="mi">80</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">score</span><span class="w"> </span><span class="k">AND</span><span class="w"> </span><span class="n">score</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="mi">90</span><span class="w"> </span><span class="k">THEN</span><span class="w"> </span><span class="s1">'GOOD'</span><span class="w"> </span><span class="k">ELSE</span><span class="w"> </span><span class="s1">'BAD'</span><span class="w"> </span><span class="k">END</span><span class="w"> </span><span class="k">AS</span><span class="w"> </span><span class="k">level</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">student</span><span class="p">;</span>
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</pre></div></td></tr></table></div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="dli_08_0187.html">CASE...WHEN</a></div>
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