SQLSERVER实现更改表名，更改列名，更改约束代码

sp_rename tablename,newtablename 

sp_rename 'tablename.colname',newcolname,'column' 

ALTER TABLE student Add nationality varchar(20)

alter table student add studentName int default 0 --示例3 添加int类型的列,默认值为0，主键 
alter table student add studentId int primary key default 0 --示例4 判断student中是否存在name字段且删除字段 
if exists(select * from syscolumns where id=object_id('student') and name='name') begin 
alter table student DROP COLUMN name 
end 

ALTER TABLE student ALTER COLUMN name VARCHAR(200) 

ALTER TABLE student DROP COLUMN nationality; 

SELECT TABLE_NAME,COLUMN_NAME,CONSTRAINT_NAME FROM information_schema.CONSTRAINT_COLUMN_USAGE
WHERE TABLE_NAME = 'student' 

SELECT TABLE_NAME, COLUMN_NAME, COLUMN_DEFAULT FROM information_schema.COLUMNS
WHERE TABLE_NAME='student' 

select name from sysobjects
where object_id('表?名?')=parent_obj and xtype='D' 

ALTER TABLE student DROP CONSTRAINT PK__student__2F36BC5B772B9A0B 

ALTER TABLE stuInfo ADD CONSTRAINT PK_stuNo PRIMARY KEY (stuNo) --示例2 添加主键约束（Primary Key）


-- 存在主键约束PK_stuNO，则删除 
IF EXISTS(SELECT * FROM sysobjects WHERE name='PK_stuNo' and xtype='PK')
Alter TABLE stuInfo
Drop Constraint PK_stuNo
Go -- 重新添加主键约束PK_stuNO 
ALTER TABLE stuInfo ADD CONSTRAINT PK_stuNo PRIMARY KEY (stuNo)
Go --示例3 添加 唯一UQ约束（Unique Constraint）
-- 存在唯一约束UQ_stuNO，则删除 
IF EXISTS(SELECT * FROM sysobjects WHERE name='UQ_stuID' and xtype='UQ')
Alter TABLE stuInfo
Drop Constraint UQ_stuID
Go 
-- 重新添加唯一约束UQ_stuID 
ALTER TABLE stuInfo ADD CONSTRAINT UQ_stuID UNIQUE (stuID) --示例4 添加默认DF约束（Default Constraint）
-- 存在默认约束UQ_stuNO，则删除 
IF EXISTS(SELECT * FROM sysobjects WHERE name='DF_stuAddress' and xtype='D')
Alter TABLE stuInfo Drop Constraint DF_stuAddress
Go -- 重新添加默认约束DF_stuAddress 
ALTER TABLE stuInfo ADD CONSTRAINT DF_stuAddress DEFAULT ('地址不详') FOR stuAddress --示例5 检查CK约束（Check Constraint）
-- 存在检查约束UQ_stuNO，则删除 
IF EXISTS(SELECT * FROM sysobjects WHERE name='CK_stuAge' and xtype='C')
Alter TABLE stuInfo Drop Cons