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>
29 lines
5.2 KiB
HTML
29 lines
5.2 KiB
HTML
<a name="dli_08_0188"></a><a name="dli_08_0188"></a>
|
|
|
|
<h1 class="topictitle1">Basic CASE Statement</h1>
|
|
<div id="body8662426"><div class="section" id="dli_08_0188__en-us_topic_0093947026_s753e1e6356e8491e80cf3a312d686bb1"><h4 class="sectiontitle">Function</h4><p id="dli_08_0188__en-us_topic_0093947026_a0d81b304c3d94f1d8caef0f40a23dc85">This statement is used to display <strong id="dli_08_0188__en-us_topic_0093947026_en-us_topic_0047959841_en-us_topic_0039551598_b198815279470">result_expression</strong> according to the joined results of <strong id="dli_08_0188__en-us_topic_0093947026_en-us_topic_0047959841_en-us_topic_0039551598_b447160169470">input_expression</strong> and <strong id="dli_08_0188__en-us_topic_0093947026_en-us_topic_0047959841_en-us_topic_0039551598_b668998279470">when_expression</strong>.</p>
|
|
</div>
|
|
<div class="section" id="dli_08_0188__en-us_topic_0093947026_s01b2dde98a0c43f2a405f4f8e3bc6866"><h4 class="sectiontitle">Syntax</h4><div class="codecoloring" codetype="Sql" id="dli_08_0188__screen1076313319466"><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="n">input_expression</span><span class="w"> </span><span class="k">WHEN</span><span class="w"> </span><span class="n">when_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>
|
|
</pre></div></td></tr></table></div>
|
|
|
|
</div>
|
|
</div>
|
|
<div class="section" id="dli_08_0188__en-us_topic_0093947026_sb3adbb764bb2417d8e6faab78d6e6956"><h4 class="sectiontitle">Keyword</h4><p id="dli_08_0188__en-us_topic_0093947026_a19a1e9a84b81490fb45b44eda9e817fe">CASE: Subquery is supported in basic CASE statement. However, input_expression and when_expression must be joinable.</p>
|
|
</div>
|
|
<div class="section" id="dli_08_0188__en-us_topic_0093947026_s32e07352352444b8b81619e7e7343102"><h4 class="sectiontitle">Precautions</h4><p id="dli_08_0188__en-us_topic_0093947026_a47a95e52ca454d7780597d92f907453c">If there is no input_expression = when_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>
|
|
</div>
|
|
<div class="section" id="dli_08_0188__en-us_topic_0093947026_s084771b4b2d742d0a790f4235b86f0de"><h4 class="sectiontitle">Example</h4><p id="dli_08_0188__en-us_topic_0093947026_af87e5a1b224e47259d032ac6038dcbab">To return the name field and the character that is matched to id from the student table with the following matching rules, run the following statement:</p>
|
|
<ul id="dli_08_0188__en-us_topic_0093947026_u45f34cdfac1744fa9db4de38ef757392"><li id="dli_08_0188__en-us_topic_0093947026_ld79e12c790f540babbcc608ac6f2d06d">If id is 1, 'a' is returned.</li><li id="dli_08_0188__en-us_topic_0093947026_lf9023b08013248d397bdb8862113bd6b">If id is 2, 'b' is returned.</li><li id="dli_08_0188__en-us_topic_0093947026_lf010c9593a2e4bc398f57423c9a93578">If id is 3, 'c' is returned.</li><li id="dli_08_0188__en-us_topic_0093947026_la23e15ffaf85427fa1173017e60cef63">Otherwise, <strong id="dli_08_0188__en-us_topic_0093947026_en-us_topic_0047959841_en-us_topic_0039551598_b613113129470">NULL</strong> is returned.</li></ul>
|
|
<div class="codecoloring" codetype="Sql" id="dli_08_0188__screen10368114944612"><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="n">id</span><span class="w"> </span><span class="k">WHEN</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">THEN</span><span class="w"> </span><span class="s1">'a'</span><span class="w"> </span><span class="k">WHEN</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">THEN</span><span class="w"> </span><span class="s1">'b'</span><span class="w"> </span><span class="k">WHEN</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="k">THEN</span><span class="w"> </span><span class="s1">'c'</span><span class="w"> </span><span class="k">ELSE</span><span class="w"> </span><span class="k">NULL</span><span class="w"> </span><span class="k">END</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">student</span><span class="p">;</span>
|
|
</pre></div></td></tr></table></div>
|
|
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<div>
|
|
<div class="familylinks">
|
|
<div class="parentlink"><strong>Parent topic:</strong> <a href="dli_08_0187.html">CASE...WHEN</a></div>
|
|
</div>
|
|
</div>
|
|
|