Help Center> Data Warehouse Service (DWS)> Tool Guide> DSC> SQL Syntax Migration Reference> MySQL Syntax Migrating> Schema Objects and Data Definition Language (DDL)> Table (Optional Parameters and Operations)> CHANGE (Column Modification)
Updated on 2024-04-28 GMT+08:00
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CHANGE (Column Modification)

MySQL uses the CHANGE keyword to change column names and data types and set NOT NULL constraints. DSC will perform adaptation based on GaussDB(DWS) features during migration.

Input

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CREATE TABLE IF NOT EXISTS `runoob_alter_test`(
    `dataType0` varchar(128),
    `dataType1` bigint,
    `dataType2` bigint,
    `dataType3` bigint,
    `dataType4` bigint
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

## A.
ALTER TABLE runoob_alter_test CHANGE dataType1 dataType1New VARCHAR(50);

## B.
ALTER TABLE runoob_alter_test CHANGE dataType2 dataType2New VARCHAR(50) NOT NULL;

## C.
ALTER TABLE runoob_alter_test CHANGE dataType3 dataType3New VARCHAR(100) FIRST;

## D.
ALTER TABLE runoob_alter_test CHANGE dataType4 dataType4New VARCHAR(50) AFTER dataType1;

Output

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CREATE TABLE "public"."runoob_alter_test"
(
  "datatype0" VARCHAR(512),
  "datatype1" BIGINT,
  "datatype2" BIGINT,
  "datatype3" BIGINT,
  "datatype4" BIGINT
)
  WITH ( ORIENTATION = ROW, COMPRESSION = NO )
  NOCOMPRESS
  DISTRIBUTE BY HASH ("datatype0");

-- A.
ALTER TABLE "public"."runoob_alter_test" CHANGE COLUMN "datatype1" "datatype1new" VARCHAR(200) NULL DEFAULT NULL;

-- B.
ALTER TABLE "public"."runoob_alter_test" CHANGE COLUMN "datatype2" "datatype2new" VARCHAR(200) NOT NULL;

-- C.
ALTER TABLE "public"."runoob_alter_test" CHANGE COLUMN "datatype3" "datatype3new" VARCHAR(400) NULL DEFAULT NULL;

-- D.
ALTER TABLE "public"."runoob_alter_test" CHANGE COLUMN "datatype4" "datatype4new" VARCHAR(200) NULL DEFAULT NULL;