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Lu, Huayi
a24ca60074
Reviewed-by: Hasko, Vladimir <vladimir.hasko@t-systems.com> Co-authored-by: Lu, Huayi <luhuayi@huawei.com> Co-committed-by: Lu, Huayi <luhuayi@huawei.com>
34 lines
4.2 KiB
HTML
34 lines
4.2 KiB
HTML
<a name="EN-US_TOPIC_0000001145694471"></a><a name="EN-US_TOPIC_0000001145694471"></a>
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<h1 class="topictitle1">Case: Creating an Appropriate Index</h1>
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<div id="body8662426"><div class="section" id="EN-US_TOPIC_0000001145694471__s0ff15c597be0461094854e46ccc945e2"><h4 class="sectiontitle">Symptom</h4><p id="EN-US_TOPIC_0000001145694471__a82fd573e9cca4babb73403dfe8402a3a">Query the information about all personnel in the sales department.</p>
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<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001145694471__seda3c93f9bea4965805ce0d9f7628402"><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>
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<span class="normal">3</span>
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<span class="normal">4</span>
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<span class="normal">5</span>
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<span class="normal">6</span>
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<span class="normal">7</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="n">staff_id</span><span class="p">,</span><span class="n">first_name</span><span class="p">,</span><span class="n">last_name</span><span class="p">,</span><span class="n">employment_id</span><span class="p">,</span><span class="n">state_name</span><span class="p">,</span><span class="n">city</span><span class="w"> </span>
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<span class="k">FROM</span><span class="w"> </span><span class="n">staffs</span><span class="p">,</span><span class="n">sections</span><span class="p">,</span><span class="n">states</span><span class="p">,</span><span class="n">places</span><span class="w"> </span>
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<span class="k">WHERE</span><span class="w"> </span><span class="n">sections</span><span class="p">.</span><span class="n">section_name</span><span class="o">=</span><span class="s1">'Sales'</span><span class="w"> </span>
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<span class="k">AND</span><span class="w"> </span><span class="n">staffs</span><span class="p">.</span><span class="n">section_id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sections</span><span class="p">.</span><span class="n">section_id</span><span class="w"> </span>
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<span class="k">AND</span><span class="w"> </span><span class="n">sections</span><span class="p">.</span><span class="n">place_id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">places</span><span class="p">.</span><span class="n">place_id</span><span class="w"> </span>
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<span class="k">AND</span><span class="w"> </span><span class="n">places</span><span class="p">.</span><span class="n">state_id</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">states</span><span class="p">.</span><span class="n">state_id</span><span class="w"> </span>
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<span class="k">ORDER</span><span class="w"> </span><span class="k">BY</span><span class="w"> </span><span class="n">staff_id</span><span class="p">;</span><span class="w"></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="EN-US_TOPIC_0000001145694471__s7bab6b1299084552bdcc6d17e0bd68fb"><h4 class="sectiontitle">Optimization Analysis</h4><p id="EN-US_TOPIC_0000001145694471__ad6ca675a89334e8ca83aa37da9ce29a3">The original execution plan is as follows before creating the <strong id="EN-US_TOPIC_0000001145694471__b842352706172712">places.place_id</strong> and <strong id="EN-US_TOPIC_0000001145694471__b842352706172714">states.state_id</strong> indexes:</p>
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<p id="EN-US_TOPIC_0000001145694471__p94804399910"><span><img id="EN-US_TOPIC_0000001145694471__image14491340294" src="figure/en-us_image_0000001099135104.png"></span></p>
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<p id="EN-US_TOPIC_0000001145694471__a3ea033bcdcc2454a83c9e8bffdfdcbce">The optimized execution plan is as follows (two indexes have been created on the <strong id="EN-US_TOPIC_0000001145694471__b8423527061747">places.place_id</strong> and <strong id="EN-US_TOPIC_0000001145694471__b84235270617414">states.state_id</strong> columns):</p>
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<p id="EN-US_TOPIC_0000001145694471__p15769192571118"><span><img id="EN-US_TOPIC_0000001145694471__image129511926111119" src="figure/en-us_image_0000001098975116.png"></span></p>
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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="dws_04_0474.html">Optimization Cases</a></div>
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</div>
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</div>
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