文档首页> 数据仓库服务 GaussDB(DWS)> 工具指南> DSC> SQL语法迁移参考> MySQL语法迁移> 模式对象与数据定义（DDL）> 表（可选参数、操作）> 添加与删除列
更新时间：2024-04-18 GMT+08:00
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添加与删除列

MySQL添加、删除列语句与GaussDB(DWS)存在差异。DSC工具迁移时会根据GaussDB(DWS)的特性进行相应适配。

GaussDB不支持表定义中列序数的变更，工具暂不支持FRIST，AFTER特性的完整迁移。基于当前的临时方案，工具仅仅移除该关键字。

输入示例

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CREATE TABLE IF NOT EXISTS `runoob_alter_test`(
    `dataType1` int NOT NULL AUTO_INCREMENT,
    `dataType2` FLOAT(10,2),
    `dataType3` DOUBLE(20,8),
    `dataType4` TEXT NOT NULL,
    `dataType5` YEAR NOT NULL DEFAULT '2018',
    `dataType6` DATETIME NOT NULL DEFAULT '2018-10-12 15:27:33.999999',
    `dataType7` CHAR NOT NULL DEFAULT '',
    `dataType8` VARCHAR(50),
    `dataType9` VARCHAR(50) NOT NULL DEFAULT '',
    `dataType10` TIME NOT NULL DEFAULT '10:20:59',
    PRIMARY KEY(`dataType1`)
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

## A.
ALTER TABLE runoob_alter_test ADD dataType1_1 INT NOT NULL AFTER dataType1;
ALTER TABLE runoob_alter_test DROP dataType1_1;

## B.
ALTER TABLE runoob_alter_test ADD dataType1_1 INT NOT NULL FIRST;
ALTER TABLE runoob_alter_test DROP dataType1_1;

## C.
ALTER TABLE runoob_alter_test ADD COLUMN dataType1_1 INT NOT NULL AFTER dataType2;
ALTER TABLE runoob_alter_test DROP COLUMN dataType1_1;

## D.
ALTER TABLE runoob_alter_test ADD COLUMN dataType1_1 INT NOT NULL FIRST;
ALTER TABLE runoob_alter_test DROP COLUMN dataType1_1;

## E.
ALTER TABLE runoob_alter_test ADD COLUMN(dataType1_1 INT NOT NULL, dataType1_2 VARCHAR(200) NOT NULL);
ALTER TABLE runoob_alter_test DROP COLUMN dataType1_1, DROP COLUMN dataType1_2;

输出示例

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CREATE TABLE "public"."runoob_alter_test"
(
  "datatype1" SERIAL NOT NULL,
  "datatype2" REAL,
  "datatype3" DOUBLE PRECISION,
  "datatype4" TEXT NOT NULL,
  "datatype5" SMALLINT NOT NULL DEFAULT '2018',
  "datatype6" TIMESTAMP WITHOUT TIME ZONE NOT NULL DEFAULT '2018-10-12 15:27:33.999999',
  "datatype7" CHAR(4) NOT NULL DEFAULT '',
  "datatype8" VARCHAR(200),
  "datatype9" VARCHAR(200) NOT NULL DEFAULT '',
  "datatype10" TIME WITHOUT TIME ZONE NOT NULL DEFAULT '10:20:59',
  PRIMARY KEY ("datatype1")
)
  WITH ( ORIENTATION = ROW, COMPRESSION = NO )
  NOCOMPRESS
  DISTRIBUTE BY HASH ("datatype1");

-- A.
ALTER TABLE "public"."runoob_alter_test" ADD COLUMN "datatype1_1" INTEGER NOT NULL DEFAULT 0;
ALTER TABLE "public"."runoob_alter_test" DROP COLUMN "datatype1_1" RESTRICT;

-- B.
ALTER TABLE "public"."runoob_alter_test" ADD COLUMN "datatype1_1" INTEGER NOT NULL DEFAULT 0;
ALTER TABLE "public"."runoob_alter_test" DROP COLUMN "datatype1_1" RESTRICT;

-- C.
ALTER TABLE "public"."runoob_alter_test" ADD COLUMN "datatype1_1" INTEGER NOT NULL DEFAULT 0;
ALTER TABLE "public"."runoob_alter_test" DROP COLUMN "datatype1_1" RESTRICT;

-- D.
ALTER TABLE "public"."runoob_alter_test" ADD COLUMN "datatype1_1" INTEGER NOT NULL DEFAULT 0;
ALTER TABLE "public"."runoob_alter_test" DROP COLUMN "datatype1_1" RESTRICT;

-- E.
ALTER TABLE "public"."runoob_alter_test" ADD COLUMN "datatype1_1" INTEGER NOT NULL, ADD COLUMN "datatype1_2" VARCHAR(800) NOT NULL DEFAULT '';
ALTER TABLE "public"."runoob_alter_test" DROP COLUMN "datatype1_1" RESTRICT, DROP COLUMN "datatype1_2" RESTRICT;
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