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doc-exports/docs/dws/tool/dws_16_0158.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_0000001860318461"></a><a name="EN-US_TOPIC_0000001860318461"></a>
<h1 class="topictitle1">MODIFY (Modifying a Column)</h1>
<div id="body8662426"><p id="EN-US_TOPIC_0000001860318461__en-us_topic_0000001385616046_en-us_topic_0214164523_p7574545962">MySQL uses the <strong id="EN-US_TOPIC_0000001860318461__en-us_topic_0000001385616046_b1392851916511">MODIFY</strong> keyword to change column data types and set <strong id="EN-US_TOPIC_0000001860318461__en-us_topic_0000001385616046_b11929101935112">NOT NULL</strong> constraints. DSC will perform adaptation based on GaussDB(DWS) features during migration.</p>
<p id="EN-US_TOPIC_0000001860318461__en-us_topic_0000001385616046_en-us_topic_0214164523_p8822521203711"><strong id="EN-US_TOPIC_0000001860318461__en-us_topic_0000001385616046_en-us_topic_0214164523_b20727929204011">Input</strong></p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001860318461__en-us_topic_0000001385616046_en-us_topic_0214164523_screen146478312316"><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"> 4</span>
<span class="normal"> 5</span>
<span class="normal"> 6</span>
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<span class="normal">18</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="k">IF</span><span class="w"> </span><span class="k">NOT</span><span class="w"> </span><span class="k">EXISTS</span><span class="w"> </span><span class="o">`</span><span class="n">runoob_alter_test</span><span class="o">`</span><span class="p">(</span>
<span class="w"> </span><span class="o">`</span><span class="n">dataType0</span><span class="o">`</span><span class="w"> </span><span class="nb">varchar</span><span class="p">(</span><span class="mi">100</span><span class="p">),</span>
<span class="w"> </span><span class="o">`</span><span class="n">dataType1</span><span class="o">`</span><span class="w"> </span><span class="nb">bigint</span><span class="p">,</span>
<span class="w"> </span><span class="o">`</span><span class="n">dataType2</span><span class="o">`</span><span class="w"> </span><span class="nb">bigint</span><span class="p">,</span>
<span class="w"> </span><span class="o">`</span><span class="n">dataType3</span><span class="o">`</span><span class="w"> </span><span class="nb">bigint</span>
<span class="p">)</span><span class="n">ENGINE</span><span class="o">=</span><span class="n">InnoDB</span><span class="w"> </span><span class="k">DEFAULT</span><span class="w"> </span><span class="n">CHARSET</span><span class="o">=</span><span class="n">utf8</span><span class="p">;</span>
<span class="o">##</span><span class="w"> </span><span class="n">A</span><span class="p">.</span>
<span class="k">ALTER</span><span class="w"> </span><span class="k">TABLE</span><span class="w"> </span><span class="n">runoob_alter_test</span><span class="w"> </span><span class="k">MODIFY</span><span class="w"> </span><span class="n">dataType1</span><span class="w"> </span><span class="nb">smallint</span><span class="p">;</span>
<span class="o">##</span><span class="w"> </span><span class="n">B</span><span class="p">.</span>
<span class="k">ALTER</span><span class="w"> </span><span class="k">TABLE</span><span class="w"> </span><span class="n">runoob_alter_test</span><span class="w"> </span><span class="k">MODIFY</span><span class="w"> </span><span class="n">dataType1</span><span class="w"> </span><span class="nb">smallint</span><span class="w"> </span><span class="k">NOT</span><span class="w"> </span><span class="k">NULL</span><span class="p">;</span>
<span class="o">##</span><span class="w"> </span><span class="k">C</span><span class="p">.</span>
<span class="k">ALTER</span><span class="w"> </span><span class="k">TABLE</span><span class="w"> </span><span class="n">runoob_alter_test</span><span class="w"> </span><span class="k">MODIFY</span><span class="w"> </span><span class="n">dataType1</span><span class="w"> </span><span class="nb">smallint</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">FIRST</span><span class="p">;</span>
<span class="o">##</span><span class="w"> </span><span class="n">D</span><span class="p">.</span>
<span class="k">ALTER</span><span class="w"> </span><span class="k">TABLE</span><span class="w"> </span><span class="n">runoob_alter_test</span><span class="w"> </span><span class="k">MODIFY</span><span class="w"> </span><span class="n">dataType1</span><span class="w"> </span><span class="nb">smallint</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">AFTER</span><span class="w"> </span><span class="n">dataType3</span><span class="p">;</span>
</pre></div></td></tr></table></div>
</div>
<p id="EN-US_TOPIC_0000001860318461__en-us_topic_0000001385616046_en-us_topic_0214164523_p1431826173714"><strong id="EN-US_TOPIC_0000001860318461__en-us_topic_0000001385616046_en-us_topic_0214164523_b11199142516406">Output</strong></p>
<div class="codecoloring" codetype="Sql" id="EN-US_TOPIC_0000001860318461__en-us_topic_0000001385616046_en-us_topic_0214164523_screen173941613113"><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>
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<span class="normal">22</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;runoob_alter_test&quot;</span>
<span class="p">(</span>
<span class="w"> </span><span class="ss">&quot;datatype0&quot;</span><span class="w"> </span><span class="nb">VARCHAR</span><span class="p">(</span><span class="mi">400</span><span class="p">),</span>
<span class="w"> </span><span class="ss">&quot;datatype1&quot;</span><span class="w"> </span><span class="nb">BIGINT</span><span class="p">,</span>
<span class="w"> </span><span class="ss">&quot;datatype2&quot;</span><span class="w"> </span><span class="nb">BIGINT</span><span class="p">,</span>
<span class="w"> </span><span class="ss">&quot;datatype3&quot;</span><span class="w"> </span><span class="nb">BIGINT</span>
<span class="p">)</span>
<span class="w"> </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="w"> </span><span class="n">NOCOMPRESS</span>
<span class="w"> </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;datatype0&quot;</span><span class="p">);</span>
<span class="c1">-- A.</span>
<span class="k">ALTER</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;runoob_alter_test&quot;</span><span class="w"> </span><span class="k">MODIFY</span><span class="w"> </span><span class="ss">&quot;datatype1&quot;</span><span class="w"> </span><span class="nb">SMALLINT</span><span class="w"> </span><span class="k">NULL</span><span class="w"> </span><span class="k">DEFAULT</span><span class="w"> </span><span class="k">NULL</span><span class="p">;</span>
<span class="c1">-- B.</span>
<span class="k">ALTER</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;runoob_alter_test&quot;</span><span class="w"> </span><span class="k">MODIFY</span><span class="w"> </span><span class="ss">&quot;datatype1&quot;</span><span class="w"> </span><span class="nb">SMALLINT</span><span class="w"> </span><span class="k">NOT</span><span class="w"> </span><span class="k">NULL</span><span class="p">;</span>
<span class="c1">-- C.</span>
<span class="k">ALTER</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;runoob_alter_test&quot;</span><span class="w"> </span><span class="k">MODIFY</span><span class="w"> </span><span class="ss">&quot;datatype1&quot;</span><span class="w"> </span><span class="nb">SMALLINT</span><span class="w"> </span><span class="k">NOT</span><span class="w"> </span><span class="k">NULL</span><span class="p">;</span>
<span class="c1">-- D.</span>
<span class="k">ALTER</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;runoob_alter_test&quot;</span><span class="w"> </span><span class="k">MODIFY</span><span class="w"> </span><span class="ss">&quot;datatype1&quot;</span><span class="w"> </span><span class="nb">SMALLINT</span><span class="w"> </span><span class="k">NOT</span><span class="w"> </span><span class="k">NULL</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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