Help Center/ Data Warehouse Service/ Tool Guide/ DSC/ MySQL Syntax Migrating/ Table (Optional Parameters and Operations)/ MODIFY (Modifying a Column)
Updated on 2025-04-10 GMT+08:00
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MODIFY (Modifying a Column)

MySQL uses the MODIFY keyword to change column 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(100),
    `dataType1` bigint,
    `dataType2` bigint,
    `dataType3` bigint
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

## A.
ALTER TABLE runoob_alter_test MODIFY dataType1 smallint;

## B.
ALTER TABLE runoob_alter_test MODIFY dataType1 smallint NOT NULL;

## C.
ALTER TABLE runoob_alter_test MODIFY dataType1 smallint NOT NULL FIRST;

## D.
ALTER TABLE runoob_alter_test MODIFY dataType1 smallint NOT NULL AFTER dataType3;

Output

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CREATE TABLE "public"."runoob_alter_test"
(
  "datatype0" VARCHAR(400),
  "datatype1" BIGINT,
  "datatype2" BIGINT,
  "datatype3" BIGINT
)
  WITH ( ORIENTATION = ROW, COMPRESSION = NO )
  NOCOMPRESS
  DISTRIBUTE BY HASH ("datatype0");

-- A.
ALTER TABLE "public"."runoob_alter_test" MODIFY "datatype1" SMALLINT NULL DEFAULT NULL;

-- B.
ALTER TABLE "public"."runoob_alter_test" MODIFY "datatype1" SMALLINT NOT NULL;

-- C.
ALTER TABLE "public"."runoob_alter_test" MODIFY "datatype1" SMALLINT NOT NULL;

-- D.
ALTER TABLE "public"."runoob_alter_test" MODIFY "datatype1" SMALLINT NOT NULL;