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doc-exports/docs/dws/tool/dws_16_0152.html
luhuayi a5e3903f6b DWS TG 910.211 version 
Reviewed-by: Pruthi, Vineet <vineet.pruthi@t-systems.com>
Co-authored-by: luhuayi <luhuayi@huawei.com>
Co-committed-by: luhuayi <luhuayi@huawei.com>
2025-04-23 13:53:01 +00:00

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<a name="EN-US_TOPIC_0000001860318541"></a><a name="EN-US_TOPIC_0000001860318541"></a>
<h1 class="topictitle1">UNION</h1>
<div id="body8662426"><p id="EN-US_TOPIC_0000001860318541__en-us_topic_0000001385456450_p4248204901710"><strong id="EN-US_TOPIC_0000001860318541__en-us_topic_0000001385456450_b2197346633181">UNION</strong> is a table creation parameter of the MERGE storage engine. Creating a table using this keyword is similar to creating a common view. The created table logically combines the data of multiple tables that are specified by UNION. DSC migrates this feature to the view creation statement in GaussDB.</p>
<p id="EN-US_TOPIC_0000001860318541__en-us_topic_0000001385456450_en-us_topic_0214164504_p524954714513"><strong id="EN-US_TOPIC_0000001860318541__en-us_topic_0000001385456450_en-us_topic_0214164504_b39993815565">Input</strong></p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001860318541__en-us_topic_0000001385456450_en-us_topic_0214164504_screen48015451078"><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>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span>
<span class="normal">12</span>
<span class="normal">13</span>
<span class="normal">14</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">CREATE</span><span class="w"> </span><span class="k">TABLE</span><span class="w"> </span><span class="n">t1</span><span class="w"> </span><span class="p">(</span>
<span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="nb">INT</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="n">AUTO_INCREMENT</span><span class="w"> </span><span class="k">PRIMARY</span><span class="w"> </span><span class="k">KEY</span><span class="p">,</span>
<span class="w"> </span><span class="n">message</span><span class="w"> </span><span class="nb">CHAR</span><span class="p">(</span><span class="mi">20</span><span class="p">)</span>
<span class="p">)</span><span class="w"> </span><span class="n">ENGINE</span><span class="o">=</span><span class="n">MyISAM</span><span class="p">;</span>
<span class="k">CREATE</span><span class="w"> </span><span class="k">TABLE</span><span class="w"> </span><span class="n">t2</span><span class="w"> </span><span class="p">(</span>
<span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="nb">INT</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="n">AUTO_INCREMENT</span><span class="w"> </span><span class="k">PRIMARY</span><span class="w"> </span><span class="k">KEY</span><span class="p">,</span>
<span class="w"> </span><span class="n">message</span><span class="w"> </span><span class="nb">CHAR</span><span class="p">(</span><span class="mi">20</span><span class="p">)</span>
<span class="p">)</span><span class="w"> </span><span class="n">ENGINE</span><span class="o">=</span><span class="n">MyISAM</span><span class="p">;</span>
<span class="k">CREATE</span><span class="w"> </span><span class="k">TABLE</span><span class="w"> </span><span class="n">total</span><span class="w"> </span><span class="p">(</span>
<span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="nb">INT</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="n">AUTO_INCREMENT</span><span class="p">,</span>
<span class="w"> </span><span class="n">message</span><span class="w"> </span><span class="nb">CHAR</span><span class="p">(</span><span class="mi">20</span><span class="p">))</span>
<span class="n">ENGINE</span><span class="o">=</span><span class="n">MyISAM</span><span class="w"> </span><span class="k">UNION</span><span class="o">=</span><span class="p">(</span><span class="n">t1</span><span class="p">,</span><span class="n">t2</span><span class="p">)</span><span class="w"> </span><span class="n">INSERT_METHOD</span><span class="o">=</span><span class="k">LAST</span><span class="p">;</span>
</pre></div></td></tr></table></div>
</div>
<p id="EN-US_TOPIC_0000001860318541__en-us_topic_0000001385456450_en-us_topic_0214164504_p12114173518210"><strong id="EN-US_TOPIC_0000001860318541__en-us_topic_0000001385456450_en-us_topic_0214164504_b424094218566">Output</strong></p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001860318541__en-us_topic_0000001385456450_en-us_topic_0214164504_screen1145484581614"><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>
<span class="normal"> 9</span>
<span class="normal">10</span>
<span class="normal">11</span>
<span class="normal">12</span>
<span class="normal">13</span>
<span class="normal">14</span>
<span class="normal">15</span>
<span class="normal">16</span>
<span class="normal">17</span>
<span class="normal">18</span>
<span class="normal">19</span>
<span class="normal">20</span></pre></div></td><td class="code"><div><pre><span></span><span class="k">CREATE</span><span class="w"> </span><span class="k">TABLE</span><span class="w"> </span><span class="ss">&quot;public&quot;</span><span class="p">.</span><span class="ss">&quot;t1&quot;</span><span class="w"> </span><span class="p">(</span>
<span class="w"> </span><span class="ss">&quot;a&quot;</span><span class="w"> </span><span class="nb">SERIAL</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">PRIMARY</span><span class="w"> </span><span class="k">KEY</span><span class="p">,</span>
<span class="w"> </span><span class="ss">&quot;message&quot;</span><span class="w"> </span><span class="nb">CHAR</span><span class="p">(</span><span class="mi">80</span><span class="p">)</span>
<span class="p">)</span>
<span class="k">WITH</span><span class="w"> </span><span class="p">(</span><span class="w"> </span><span class="n">ORIENTATION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">ROW</span><span class="p">,</span><span class="w"> </span><span class="n">COMPRESSION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">NO</span><span class="w"> </span><span class="p">)</span>
<span class="n">NOCOMPRESS</span>
<span class="n">DISTRIBUTE</span><span class="w"> </span><span class="k">BY</span><span class="w"> </span><span class="n">HASH</span><span class="w"> </span><span class="p">(</span><span class="ss">&quot;a&quot;</span><span class="p">);</span>
<span class="k">CREATE</span><span class="w"> </span><span class="k">TABLE</span><span class="w"> </span><span class="ss">&quot;public&quot;</span><span class="p">.</span><span class="ss">&quot;t2&quot;</span><span class="w"> </span><span class="p">(</span>
<span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="nb">SERIAL</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">PRIMARY</span><span class="w"> </span><span class="k">KEY</span><span class="p">,</span>
<span class="w"> </span><span class="n">message</span><span class="w"> </span><span class="nb">CHAR</span><span class="p">(</span><span class="mi">80</span><span class="p">)</span>
<span class="p">)</span>
<span class="k">WITH</span><span class="w"> </span><span class="p">(</span><span class="w"> </span><span class="n">ORIENTATION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">ROW</span><span class="p">,</span><span class="w"> </span><span class="n">COMPRESSION</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">NO</span><span class="w"> </span><span class="p">)</span>
<span class="n">NOCOMPRESS</span>
<span class="n">DISTRIBUTE</span><span class="w"> </span><span class="k">BY</span><span class="w"> </span><span class="n">HASH</span><span class="w"> </span><span class="p">(</span><span class="ss">&quot;a&quot;</span><span class="p">);</span>
<span class="k">CREATE</span><span class="w"> </span><span class="k">VIEW</span><span class="w"> </span><span class="ss">&quot;public&quot;</span><span class="p">.</span><span class="ss">&quot;total&quot;</span><span class="p">(</span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="n">message</span><span class="p">)</span><span class="w"> </span><span class="k">AS</span>
<span class="k">SELECT</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="ss">&quot;public&quot;</span><span class="p">.</span><span class="ss">&quot;t1&quot;</span>
<span class="k">UNION</span><span class="w"> </span><span class="k">ALL</span>
<span class="k">SELECT</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="k">FROM</span><span class="w"> </span><span class="ss">&quot;public&quot;</span><span class="p">.</span><span class="ss">&quot;t2&quot;</span><span class="p">;</span>
</pre></div></td></tr></table></div>
</div>
</div>
<div>
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="dws_16_0119.html">Table (Optional Parameters and Operations)</a></div>
</div>
</div>
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