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Lu, Huayi a24ca60074 DWS DEVELOPER 811 version 
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>
2023-01-19 13:37:49 +00:00

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<a name="EN-US_TOPIC_0000001145710839"></a><a name="EN-US_TOPIC_0000001145710839"></a>
<h1 class="topictitle1">Simple Expressions</h1>
<div id="body8662426"><div class="section" id="EN-US_TOPIC_0000001145710839__s256c6032aa374037a04f5073012f2702"><h4 class="sectiontitle">Logical Expressions</h4><p id="EN-US_TOPIC_0000001145710839__a26a28589d465479797b2ff5955a042d9"><a href="dws_06_0028.html">Logical Operators</a> lists the operators and calculation rules of logical expressions.</p>
</div>
<div class="section" id="EN-US_TOPIC_0000001145710839__s830e997afb20461f8059daba265149ff"><h4 class="sectiontitle">Comparative Expressions</h4><p id="EN-US_TOPIC_0000001145710839__a44202e9d9ce043f3a6beb6527cd7be41"><a href="dws_06_0029.html">Comparison Operators</a> lists the common comparative operators.</p>
<p id="EN-US_TOPIC_0000001145710839__a0cdc61703cad48cc889cab4a23cb41b8">In addition to comparative operators, you can also use the following sentence structure:</p>
<ul id="EN-US_TOPIC_0000001145710839__ud3f4677ec33a4a3caf092c48a9fd89f8"><li id="EN-US_TOPIC_0000001145710839__l99048c7decee4955bb60f6d31b2a930f">BETWEEN operator<p id="EN-US_TOPIC_0000001145710839__adaf012a70d604328bf70bcd63ebb946a"><a name="EN-US_TOPIC_0000001145710839__l99048c7decee4955bb60f6d31b2a930f"></a><a name="l99048c7decee4955bb60f6d31b2a930f"></a><strong id="EN-US_TOPIC_0000001145710839__b84235270620354">a BETWEEN x<em id="EN-US_TOPIC_0000001145710839__i136301522020352"> </em> AND y</strong> is equivalent to <strong id="EN-US_TOPIC_0000001145710839__b84235270620358">a &gt;= x AND a &lt;= y</strong>.</p>
<p id="EN-US_TOPIC_0000001145710839__a63a9897ab84d4e40be6c1ec57647957a"><strong id="EN-US_TOPIC_0000001145710839__b8423527062047">a NOT BETWEEN<em id="EN-US_TOPIC_0000001145710839__i67082715"></em> x AND y</strong> is equivalent to <strong id="EN-US_TOPIC_0000001145710839__b84235270620414">a &lt; x OR a &gt; y</strong>.</p>
</li><li id="EN-US_TOPIC_0000001145710839__ld159d58d830a4a6ab1fb329e3e78ac1a">To check whether a value is null, use:<p id="EN-US_TOPIC_0000001145710839__a8db34b14798b4ca9ad31b81bd9978e94"><a name="EN-US_TOPIC_0000001145710839__ld159d58d830a4a6ab1fb329e3e78ac1a"></a><a name="ld159d58d830a4a6ab1fb329e3e78ac1a"></a>expression<em id="EN-US_TOPIC_0000001145710839__a0b1eac2d0253470ab03c0815524a3373"> </em>IS NULL</p>
<p id="EN-US_TOPIC_0000001145710839__a6c96bca28a724687836a6f9761d1f169">expression IS NOT NULL</p>
<p id="EN-US_TOPIC_0000001145710839__a58e70477bccd41dd8bcd79a7e2e2733c">or an equivalent (non-standard) sentence structure:</p>
<p id="EN-US_TOPIC_0000001145710839__a04bd919636364457814f51e761c4330c">expression<em id="EN-US_TOPIC_0000001145710839__af6085b891e71472590da7c3d778f02b0"> </em> ISNULL</p>
<p id="EN-US_TOPIC_0000001145710839__aff96043625bc432eb167b1edcc722419">expression NOTNULL</p>
<div class="notice" id="EN-US_TOPIC_0000001145710839__nc11565216db546a6ab70592c1d903892"><span class="noticetitle"><img src="public_sys-resources/notice_3.0-en-us.png"> </span><div class="noticebody"><p id="EN-US_TOPIC_0000001145710839__af75c0018c9f948209f07aceed52a22d2">Do not write <strong id="EN-US_TOPIC_0000001145710839__b52414719510">expression=NULL</strong> or <strong id="EN-US_TOPIC_0000001145710839__b122604410517">expression&lt;&gt;(!=)NULL</strong>, because <strong id="EN-US_TOPIC_0000001145710839__b62141141345">NULL</strong> represents an unknown value, and these expressions cannot determine whether two unknown values are equal.</p>
</div></div>
</li></ul>
</div>
<div class="section" id="EN-US_TOPIC_0000001145710839__s226d2ccf1fcf4f18bc62404fb52de829"><h4 class="sectiontitle">Examples</h4><div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001145710839__s3dea1a3b223141b68ef9ffa9c3efa768"><div class="highlight"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><span class="normal"> 1</span>
<span class="normal"> 2</span>
<span class="normal"> 3</span>
<span class="normal"> 4</span>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
<span class="normal"> 7</span>
<span class="normal"> 8</span>
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<span class="normal">30</span>
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<span class="normal">59</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">SELECT</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">BETWEEN</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">AND</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="k">AS</span><span class="w"> </span><span class="k">RESULT</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="k">result</span><span class="w"> </span>
<span class="c1">----------</span>
<span class="w"> </span><span class="n">t</span><span class="w"></span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span><span class="w"></span>
<span class="k">SELECT</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">AND</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="k">AS</span><span class="w"> </span><span class="k">RESULT</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="k">result</span><span class="w"> </span>
<span class="c1">----------</span>
<span class="w"> </span><span class="n">t</span><span class="w"></span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span><span class="w"></span>
<span class="k">SELECT</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="k">NOT</span><span class="w"> </span><span class="k">BETWEEN</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">AND</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="k">AS</span><span class="w"> </span><span class="k">RESULT</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="k">result</span><span class="w"> </span>
<span class="c1">----------</span>
<span class="w"> </span><span class="n">f</span><span class="w"></span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span><span class="w"></span>
<span class="k">SELECT</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="k">OR</span><span class="w"> </span><span class="mi">2</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="mi">3</span><span class="w"> </span><span class="k">AS</span><span class="w"> </span><span class="k">RESULT</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="k">result</span><span class="w"> </span>
<span class="c1">----------</span>
<span class="w"> </span><span class="n">f</span><span class="w"></span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span><span class="w"></span>
<span class="k">SELECT</span><span class="w"> </span><span class="mi">2</span><span class="o">+</span><span class="mi">2</span><span class="w"> </span><span class="k">IS</span><span class="w"> </span><span class="k">NULL</span><span class="w"> </span><span class="k">AS</span><span class="w"> </span><span class="k">RESULT</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="k">result</span><span class="w"> </span>
<span class="c1">----------</span>
<span class="w"> </span><span class="n">f</span><span class="w"></span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span><span class="w"></span>
<span class="k">SELECT</span><span class="w"> </span><span class="mi">2</span><span class="o">+</span><span class="mi">2</span><span class="w"> </span><span class="k">IS</span><span class="w"> </span><span class="k">NOT</span><span class="w"> </span><span class="k">NULL</span><span class="w"> </span><span class="k">AS</span><span class="w"> </span><span class="k">RESULT</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="k">result</span><span class="w"> </span>
<span class="c1">----------</span>
<span class="w"> </span><span class="n">t</span><span class="w"></span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span><span class="w"></span>
<span class="k">SELECT</span><span class="w"> </span><span class="mi">2</span><span class="o">+</span><span class="mi">2</span><span class="w"> </span><span class="k">ISNULL</span><span class="w"> </span><span class="k">AS</span><span class="w"> </span><span class="k">RESULT</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="k">result</span><span class="w"> </span>
<span class="c1">----------</span>
<span class="w"> </span><span class="n">f</span><span class="w"></span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span><span class="w"></span>
<span class="k">SELECT</span><span class="w"> </span><span class="mi">2</span><span class="o">+</span><span class="mi">2</span><span class="w"> </span><span class="k">NOTNULL</span><span class="w"> </span><span class="k">AS</span><span class="w"> </span><span class="k">RESULT</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="k">result</span><span class="w"> </span>
<span class="c1">----------</span>
<span class="w"> </span><span class="n">t</span><span class="w"></span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span><span class="w"></span>
<span class="k">SELECT</span><span class="w"> </span><span class="mi">2</span><span class="o">+</span><span class="mi">2</span><span class="w"> </span><span class="k">IS</span><span class="w"> </span><span class="k">DISTINCT</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="k">NULL</span><span class="w"> </span><span class="k">AS</span><span class="w"> </span><span class="k">RESULT</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="k">result</span><span class="w"> </span>
<span class="c1">----------</span>
<span class="w"> </span><span class="n">t</span><span class="w"></span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span><span class="w"></span>
<span class="k">SELECT</span><span class="w"> </span><span class="mi">2</span><span class="o">+</span><span class="mi">2</span><span class="w"> </span><span class="k">IS</span><span class="w"> </span><span class="k">NOT</span><span class="w"> </span><span class="k">DISTINCT</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="k">NULL</span><span class="w"> </span><span class="k">AS</span><span class="w"> </span><span class="k">RESULT</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="k">result</span><span class="w"> </span>
<span class="c1">----------</span>
<span class="w"> </span><span class="n">f</span><span class="w"></span>
<span class="p">(</span><span class="mi">1</span><span class="w"> </span><span class="k">row</span><span class="p">)</span><span class="w"></span>
</pre></div></td></tr></table></div>
</div>
</div>
</div>
<div>
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="dws_06_0069.html">Expressions</a></div>
</div>
</div>
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