forked from docs/doc-exports
Lu, Huayi
27019c2991
Reviewed-by: Hasko, Vladimir <vladimir.hasko@t-systems.com> Reviewed-by: Pruthi, Vineet <vineet.pruthi@t-systems.com> Co-authored-by: Lu, Huayi <luhuayi@huawei.com> Co-committed-by: Lu, Huayi <luhuayi@huawei.com>
56 lines
3.0 KiB
HTML
56 lines
3.0 KiB
HTML
<a name="EN-US_TOPIC_0000001772696200"></a><a name="EN-US_TOPIC_0000001772696200"></a>
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<h1 class="topictitle1">CHANGE (Column Modification)</h1>
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<div id="body8662426"><p id="EN-US_TOPIC_0000001772696200__en-us_topic_0000001706105097_en-us_topic_0000001435896193_en-us_topic_0214164478_p2091463310273">MySQL uses the <strong id="EN-US_TOPIC_0000001772696200__en-us_topic_0000001706105097_en-us_topic_0000001435896193_b163109132231650">CHANGE</strong> keyword to change column names and data types and set <strong id="EN-US_TOPIC_0000001772696200__en-us_topic_0000001706105097_en-us_topic_0000001435896193_b114709199431650">NOT NULL</strong> constraints. DSC will perform adaptation based on GaussDB(DWS) features during migration.</p>
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<p id="EN-US_TOPIC_0000001772696200__en-us_topic_0000001706105097_en-us_topic_0000001435896193_en-us_topic_0214164478_p8060118"><strong id="EN-US_TOPIC_0000001772696200__en-us_topic_0000001706105097_en-us_topic_0000001435896193_en-us_topic_0214164478_b20727929204011">Input</strong></p>
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<pre class="screen" id="EN-US_TOPIC_0000001772696200__en-us_topic_0000001706105097_en-us_topic_0000001435896193_en-us_topic_0214164478_screen897275693011">CREATE TABLE IF NOT EXISTS `runoob_alter_test`(
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`dataType0` varchar(128),
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`dataType1` bigint,
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`dataType2` bigint,
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`dataType3` bigint,
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`dataType4` bigint
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)ENGINE=InnoDB DEFAULT CHARSET=utf8;
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## A.
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ALTER TABLE runoob_alter_test CHANGE dataType1 dataType1New VARCHAR(50);
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## B.
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ALTER TABLE runoob_alter_test CHANGE dataType2 dataType2New VARCHAR(50) NOT NULL;
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## C.
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ALTER TABLE runoob_alter_test CHANGE dataType3 dataType3New VARCHAR(100) FIRST;
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## D.
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ALTER TABLE runoob_alter_test CHANGE dataType4 dataType4New VARCHAR(50) AFTER dataType1;</pre>
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<p id="EN-US_TOPIC_0000001772696200__en-us_topic_0000001706105097_en-us_topic_0000001435896193_en-us_topic_0214164478_p1431826173714"><strong id="EN-US_TOPIC_0000001772696200__en-us_topic_0000001706105097_en-us_topic_0000001435896193_en-us_topic_0214164478_b11199142516406">Output</strong></p>
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<pre class="screen" id="EN-US_TOPIC_0000001772696200__en-us_topic_0000001706105097_en-us_topic_0000001435896193_en-us_topic_0214164478_screen1573016073113">CREATE TABLE "public"."runoob_alter_test"
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(
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"datatype0" VARCHAR(512),
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"datatype1" BIGINT,
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"datatype2" BIGINT,
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"datatype3" BIGINT,
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"datatype4" BIGINT
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)
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WITH ( ORIENTATION = ROW, COMPRESSION = NO )
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NOCOMPRESS
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DISTRIBUTE BY HASH ("datatype0");
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-- A.
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ALTER TABLE "public"."runoob_alter_test" CHANGE COLUMN "datatype1" "datatype1new" VARCHAR(200) NULL DEFAULT NULL;
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-- B.
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ALTER TABLE "public"."runoob_alter_test" CHANGE COLUMN "datatype2" "datatype2new" VARCHAR(200) NOT NULL;
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-- C.
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ALTER TABLE "public"."runoob_alter_test" CHANGE COLUMN "datatype3" "datatype3new" VARCHAR(400) NULL DEFAULT NULL;
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-- D.
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ALTER TABLE "public"."runoob_alter_test" CHANGE COLUMN "datatype4" "datatype4new" VARCHAR(200) NULL DEFAULT NULL;</pre>
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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_16_0119.html">Table (Optional Parameters and Operations)</a></div>
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</div>
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</div>
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