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
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