SQL Server中多对多关系的实现

多对多的关系必须另外添加一张表来表示

--班级
create table banji
(
	banji_id int constraint PK_banji primary key,  --主键
	banji_num int not null,
	banji_name nvarchar(20) 
)

--教师
create table jiaoshi
(
	jiaoshi_id int constraint PK_jaioshi primary key,  --主键
	jiaoshi_name nvarchar(20) not null
)

--班级和教师的关系
create table banji_jiaoshi_mapping
(
	banji_id int constraint FK_bnaji_id foreign key references banji(banji_id),    --外键
	jiaoshi_id int constraint FK_jaoshi_id foreign key references jiaoshi(jiaoshi_id),   --外键
	kecheng nvarchar(20),
	constraint PK_banji_id_jiaoshi_id primary key (banji_id, jiaoshi_id, kecheng)    --benji_id, jiaoshi_id, kecheng的三者组合作为主键
)

数据库关系图：