SQL语法基础

--创建表的同时创建约束

use tempdb

if Object_ID('testDB') is not Null

drop table testDB;

CREATE TABLE testDB(

ID INT IDENTITY(1,1) NOT NULL,

[Name] NVARCHAR(50) NOT NULL ,

Description NVARCHAR(2000) NOT NULL,

CreateDate Datetime Default(getDate()),

CONSTRAINT PK_ID PRIMARY KEY CLUSTERED (ID ASC),

CONSTRAINT CHK_ID Check (ID between 1 and 1000)

)

--删除约束

use tempdb

alter Table testDB Drop Constraint PK_ID

--修改约束

use tempdb

alter Table testDB Add Constraint PK_ID Primary key CLUSTERED(ID ASC)

1:约束格式

CONSTRAINT Constraint_name Constraint_type(col)

Constraint_type:check,Primary key,Foreign key,unique