default约束

你插入数据的时候，不手动填这个字段，数据库就自动帮你填上提前设定好的默认值，不用你每次都重复写。

create table student
(
stu_id int primary key,
stu_sal int check (stu_sal>=1000 and stu_sal<=12000),
stu_sex nchar(1) default('男')

)

insert into student(stu_id,stu_sal) values(1,1000);
insert into student values(2,10000,'女');
insert into student values(2,6000,'女');
insert into student values(4,6000,'女');
insert into student values(3,6000);