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
4.1 KiB
HTML
32 lines
4.1 KiB
HTML
<a name="dli_08_0167"></a><a name="dli_08_0167"></a>
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<h1 class="topictitle1">LEFT OUTER JOIN</h1>
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<div id="body8662426"><div class="section" id="dli_08_0167__en-us_topic_0093946788_sf53bf7b3fb304fbda9a7216661a9f393"><h4 class="sectiontitle">Function</h4><p id="dli_08_0167__en-us_topic_0093946788_ab24e0e1ab1544fadafb73f5c777a87e6">Join the left table with the right table and return all joined records of the left table. If no joined record is found, NULL will be returned. </p>
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</div>
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<div class="section" id="dli_08_0167__en-us_topic_0093946788_s9ab3b7074a84418888c70b17a65e3fe3"><h4 class="sectiontitle">Syntax</h4><div class="codecoloring" codetype="Sql" id="dli_08_0167__screen1966891443113"><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">attr_expr_list</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="n">table_reference</span>
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<span class="w"> </span><span class="k">LEFT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">table_reference</span><span class="w"> </span><span class="k">ON</span><span class="w"> </span><span class="n">join_condition</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_0167__en-us_topic_0093946788_s97430606026e47008d2bda17b225a5cb"><h4 class="sectiontitle">Keyword</h4><p id="dli_08_0167__en-us_topic_0093946788_acec4658e8f6048dc80200ed7ff1191e6">LEFT OUTER JOIN: Returns all joined records of the left table. If no record is matched, NULL is returned.</p>
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</div>
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<div class="section" id="dli_08_0167__en-us_topic_0093946788_sa378b734a37f4c19bf86c576d1eb2f80"><h4 class="sectiontitle">Precautions</h4><p id="dli_08_0167__en-us_topic_0093946788_acbfee4d46d9741f5a82ff82a6ff244e0">The to-be-joined table must exist. Otherwise, an error is reported.</p>
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</div>
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<div class="section" id="dli_08_0167__en-us_topic_0093946788_s9bfb7d5eb4b94599bf6465dd2ec9e1bd"><h4 class="sectiontitle">Example</h4><p id="dli_08_0167__en-us_topic_0093946788_ae1c58f76c43e47e2b84df2f2a071dfe2">To join the courseId from the <strong id="dli_08_0167__b13474195618012">student_info</strong> table to the <strong id="dli_08_0167__b192191031112">courseId</strong> from the <strong id="dli_08_0167__b174501288113">course_info</strong> table for inner join and return the name of the students who have selected course, run the following statement. If no joined record is found, NULL will be returned. </p>
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<div class="codecoloring" codetype="Sql" id="dli_08_0167__screen18158137133119"><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>
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<span class="w"> </span><span class="k">LEFT</span><span class="w"> </span><span class="k">OUTER</span><span class="w"> </span><span class="k">JOIN</span><span class="w"> </span><span class="n">course_info</span><span class="w"> </span><span class="k">ON</span><span class="w"> </span><span class="p">(</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>
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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="dli_08_0165.html">JOIN</a></div>
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</div>
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</div>
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