数据库手动设置数据约束

数据库手动设置数据约束

 

1手动添加[主键约束]PK_Employees_EmpId

alter table Employees add constraint PK_Employees_EmpId primary key(EmpId)

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2手动为EmpName增加非空约束

alter table Employees alter column EmpName varchar(50) not null

 

3手动为EmpName增加唯一键约束

alter table Employees add constraint UQ_Employees_EmpName unique(EmpName)

go

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4删除唯一键约束

alter table Employees drop constraint UQ_Employees_EmpName 

 

5为性别增加默认约束,使默认值为"男"

alter table Employees add constraint DF_Employees_EmpGender

default(1) for EmpGender

 

6为年龄增加检测约束  0-120含0和120

alter table Employees add constraint CK_Employees_EmpAge

check(EmpAge>=0 and EmpAge<=120)

 

7为性别增加检查约束 非 男 即 女

alter table Employees add constraint CK_Employees_EmpGender

check(EmpGender='男' or EmpGender='女')

 

8--为员工表增加外键约束

--首先，设置部门表中的DepId为主键,并且外键不能为空

alter table Department add constraint Pk_Deparment_DepId primary key(DepId)

alter table Employee alter column DepId int not null

 

alter table Employee add constraint FK_Employee_EmpDepId

foreign key(DepId) references Department(DepId) on delete cascade

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9一条语句删除多个约束

alter table Employees drop constraint FK_Employees_EmpDepId,

CK_Employees_EmpAge,

UQ_Employees_EmpName

 

10一条语句为表增加多个约束

 

alter table Employees add constraint

UQ_Employees_EmpName

unique(EmpName),

constraint

CKSSS

check(EmpAge>=0and EmpAge<=120)