create database people//创建一个数据库
create table deji//创建一个表
(
did char(12) primary key,//登记的id,char型可以存121为是主键
dname nchar(8) not null,
dsex nchar(2) check(dsex = ‘男’ or dsex = ‘女’)//check自定义限制条件
)
create table class
(
cid int primary key,
cname nvarchar(10),
ccredit int check(ccredit > 0 and ccredit <= 9),
)
create table grade
(
did char(12) foreign key references deji(did),//foreign ke 外键
cid int foreign key references class(cid),
ggrade int check(ggrade >= 0 and ggrade <= 100)
)
create table cg
(
gid int identity(1,2) primary key,
did char(12) foreign key references deji(did),
cid int foreign key references class(cid),
psgrade int,
qmgrade int,
zgrade as (psgrade + qmgrade) / 2//直接计算
)