SQLserver 创建表，设置约束

use srs 
create table s
(sno varchar(6) primary key,--主码
sn nvarchar(10) not null unique, --唯一约束
sex nchar(1) not null default ('男'),--默认
dapt nvarchar(20),
age  int)
--...............................................................................................
use srs 
create table c
(cno varchar(10) primary key,--主码
cn nvarchar(20) not null, --唯一约束),
credit  int not null)

--...............................................................................................
use srs 
create table sc
(sno varchar(6)  foreign key references s(sno), --外键，关联表
cno varchar(10)  foreign key references c(cno),
grade numeric(4,1) check (grade>=0 and grade<=100),--检查约束
primary key (sno,cno))
--....................................................................................................