SQL 常用的命令
--修改表名
--格式：SP_RENAME TABLENAME,NEWTABLENAME
SP_RENAME TABLENAME,NEWTABLENAME
--只能對表，不能對臨時表
--修改字段名
--格式：SP_RENAME ‘TABLENAME.COLNAME‘,NEWCOLNAME,‘COLUMN‘
SP_RENAME ‘TABLENAME.COLNAME‘,NEWCOLNAME,‘COLUMN‘
--添加字段
--格式：ALTER TABLE TABLE_NAME ADD NEW_COLUMN DATA_TYPE [INTERALITY_CODITION]
示例1
ALTER TABLE STUDENT ADD NATIONALITY VARCHAR(20)
ALTER TABLE STUDENT ADD ID IDENTITY INT(1,1)
--示例2 添加INT類型的列,默認值為 0
ALTER TABLE STUDENT ADD STUDENTNAME INT DEFAULT 0
--示例3 添加INT類型的列,默認值為0，主鍵
ALTER TABLE STUDENT ADD STUDENTID INT PRIMARY KEY DEFAULT 0
--示例4 判斷STUDENT中是否存在NAME字段且刪除字段
IF EXISTS(SELECT * FROM SYSCOLUMNS WHERE ID=OBJECT_ID(‘STUDENT‘) AND NAME=‘NAME‘) BEGIN
ALTER TABLE STUDENT DROP COLUMN NAME
END
更改字段
格式：ALTER TABLE TABLE_NAME ALTER COLUMN COLUMN_NAME
ALTER TABLE STUDENT ALTER COLUMN NAME VARCHAR(200)
刪除字段
格式：ALTER TABLE TABLE_NAME DROP COLUMN COLUMN_NAME
ALTER TABLE STUDENT DROP COLUMN NATIONALITY;
查看字段約束
格式： SELECT * FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE WHERE TABLE_NAME = TABLE_NAME
SELECT TABLE_NAME,COLUMN_NAME,CONSTRAINT_NAME FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE
WHERE TABLE_NAME = ‘STUDENT‘
查看字段缺省約束表達式 （即默認值等）
格式：SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = TABLE_NAME
SELECT TABLE_NAME, COLUMN_NAME, COLUMN_DEFAULT FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME=‘STUDENT‘
查看字段缺省約束名
格式：SELECT NAME FROM SYSOBJECTS WHERE OBJECT_ID(TABLE_NAME)=PARENT_OBJ AND XTYPE=’D’
SELECT NAME FROM SYSOBJECTS
WHERE OBJECT_ID(‘表?名?‘)=PARENT_OBJ AND XTYPE=‘D‘
刪除字段約束
格式：ALTER TABLE TABLENAME DROP CONSTRAINT CONSTRAINTNAME
ALTER TABLE STUDENT DROP CONSTRAINT PK__STUDENT__2F36BC5B772B9A0B
添加字段約束
格式：ALTER TABLE TABLENAME ADD CONSTRAINT CONSTRAINTNAME PRIMARY KEY (COLUMN_NAME)
--示例1
ALTER TABLE STUINFO ADD CONSTRAINT PK_STUNO PRIMARY KEY (STUNO)
--示例2 添加主鍵約束（PRIMARY KEY）
-- 存在主鍵約束PK_STUNO，則刪除
IF EXISTS(SELECT * FROM SYSOBJECTS WHERE NAME=‘PK_STUNO‘ AND XTYPE=‘PK‘)
ALTER TABLE STUINFO
DROP CONSTRAINT PK_STUNO
GO
-- 重新添加主鍵約束PK_STUNO
ALTER TABLE STUINFO ADD CONSTRAINT PK_STUNO PRIMARY KEY (STUNO)
GO
--示例3 添加 唯一UQ約束（UNIQUE CONSTRAINT）
-- 存在唯一約束UQ_STUNO，則刪除
IF EXISTS(SELECT * FROM SYSOBJECTS WHERE NAME=‘UQ_STUID‘ AND XTYPE=‘UQ‘)
ALTER TABLE STUINFO
DROP CONSTRAINT UQ_STUID
GO
-- 重新添加唯一約束UQ_STUID
ALTER TABLE STUINFO ADD CONSTRAINT UQ_STUID UNIQUE (STUID)
--示例4 添加默認DF約束（DEFAULT CONSTRAINT）
-- 存在默認約束UQ_STUNO，則刪除
IF EXISTS(SELECT * FROM SYSOBJECTS WHERE NAME=‘DF_STUADDRESS‘ AND XTYPE=‘D‘)
ALTER TABLE STUINFO DROP CONSTRAINT DF_STUADDRESS
GO
-- 重新添加默認約束DF_STUADDRESS
ALTER TABLE STUINFO ADD CONSTRAINT DF_STUADDRESS DEFAULT (‘地址不詳‘) FOR STUADDRESS
--示例5 檢查CK約束（CHECK CONSTRAINT）
-- 存在檢查約束UQ_STUNO，則刪除
IF EXISTS(SELECT * FROM SYSOBJECTS WHERE NAME=‘CK_STUAGE‘ AND XTYPE=‘C‘)
ALTER TABLE STUINFO DROP CONS
SQL 常用的命令