多對多的關係必須另外新增一張表來表示

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

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

--班級和教師的關係
create table banji_jiaoshi_mapping
(
	banji_id int constraint FK_bnaji_id foreign key references banji(banji_id),    --外來鍵
	jiaoshi_id int constraint FK_jaoshi_id foreign key references jiaoshi(jiaoshi_id),   --外來鍵
	kecheng nvarchar(20),
	constraint PK_banji_id_jiaoshi_id primary key (banji_id, jiaoshi_id, kecheng)    --benji_id, jiaoshi_id, kecheng的三者組合作為主鍵
)
 

資料庫關係圖：