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>
32 lines
4.8 KiB
HTML
32 lines
4.8 KiB
HTML
<a name="dli_08_0170"></a><a name="dli_08_0170"></a>
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<h1 class="topictitle1">IMPLICIT JOIN</h1>
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<div id="body8662426"><div class="section" id="dli_08_0170__en-us_topic_0093946955_se2247fe3f7064d7a8b254959d41f54b0"><h4 class="sectiontitle">Function</h4><p id="dli_08_0170__en-us_topic_0093946955_ae1d2a1ec480b488b871966bcf4df2475">This statement has the same function as INNER JOIN, that is, the result set that meet the WHERE condition is returned. However, IMPLICIT JOIN does not use the condition specified by JOIN.</p>
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<div class="section" id="dli_08_0170__en-us_topic_0093946955_s87ab3fc6445b48e79412f8030e9d6d36"><a name="dli_08_0170__en-us_topic_0093946955_s87ab3fc6445b48e79412f8030e9d6d36"></a><a name="en-us_topic_0093946955_s87ab3fc6445b48e79412f8030e9d6d36"></a><h4 class="sectiontitle">Syntax</h4><div class="codecoloring" codetype="Sql" id="dli_08_0170__screen1197262514332"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
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<span class="normal">2</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">table_reference</span><span class="p">.</span><span class="n">col_name</span><span class="p">,</span><span class="w"> </span><span class="n">table_reference</span><span class="p">.</span><span class="n">col_name</span><span class="p">,</span><span class="w"> </span><span class="p">...</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">table_reference</span><span class="p">,</span><span class="w"> </span><span class="n">table_reference</span>
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<span class="w"> </span><span class="k">WHERE</span><span class="w"> </span><span class="n">table_reference</span><span class="p">.</span><span class="n">col_name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">table_reference</span><span class="p">.</span><span class="n">col_name</span><span class="p">;</span>
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</pre></div></td></tr></table></div>
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</div>
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</div>
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<div class="section" id="dli_08_0170__en-us_topic_0093946955_s993a6d5dac8d45529d837231bd2e4091"><h4 class="sectiontitle">Keyword</h4><p id="dli_08_0170__en-us_topic_0093946955_aec4626de67384a2ab0dfd0e587dfd6d8">The keyword WHERE achieves the same function as JOIN...ON... and the mapped records will be returned. <a href="#dli_08_0170__en-us_topic_0093946955_s87ab3fc6445b48e79412f8030e9d6d36">Syntax</a> shows the WHERE filtering according to an equation. The WHERE filtering according to an inequation is also supported. </p>
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</div>
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<div class="section" id="dli_08_0170__en-us_topic_0093946955_s20ee4e61669f47bbb31cac45cc01e9f4"><h4 class="sectiontitle">Precautions</h4><ul id="dli_08_0170__en-us_topic_0093946955_ua1060a511e87403c958647ff57a06635"><li id="dli_08_0170__en-us_topic_0093946955_l18fdd4889d5047eb826acec738f38628">The to-be-joined table must exist. Otherwise, an error is reported.</li><li id="dli_08_0170__en-us_topic_0093946955_laae15c9b8bac45238dc1c0c9cbd0c488">The statement of IMPLICIT JOIN does not contain keywords JOIN...ON.... Instead, the WHERE clause is used as the condition to join two tables. </li></ul>
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</div>
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<div class="section" id="dli_08_0170__en-us_topic_0093946955_sc1f5631445d7480cb6d304138fec23e4"><h4 class="sectiontitle">Example</h4><p id="dli_08_0170__en-us_topic_0093946955_ab4e21a00d7ce4c00bff6782ef76016dd">To return the student names and course names that match <strong id="dli_08_0170__b48211106103">courseId</strong>, run the following statement:</p>
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<div class="codecoloring" codetype="Sql" id="dli_08_0170__screen513313534337"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal">1</span>
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<span class="normal">2</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">student_info</span><span class="p">.</span><span class="n">name</span><span class="p">,</span><span class="w"> </span><span class="n">course_info</span><span class="p">.</span><span class="n">courseName</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">student_info</span><span class="p">,</span><span class="n">course_info</span>
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<span class="w"> </span><span class="k">WHERE</span><span class="w"> </span><span class="n">student_info</span><span class="p">.</span><span class="n">courseId</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">course_info</span><span class="p">.</span><span class="n">courseId</span><span class="p">;</span>
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</pre></div></td></tr></table></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="dli_08_0165.html">JOIN</a></div>
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</div>
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</div>
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