几个数据表关系设定的问题，各位老大们帮忙呀。

[lswweb]

共四个表School(学校表)，Grade(年级表)，Subject（学校科目表），GradeSubject(年级科目表，年级科目只能在学校总科目中选择)。
这四个表设立表关系是会说产生循环或多重级联路径。要怎么修改才能成立呀。

表School
School_ID
School_Name

表Grade
Grade_ID
Grade_Name
School_ID(外键)

表Subject
Subject_ID
Subject_Name
School_ID(外键)

表GradeSubject
GS_ID
Grade_ID(外键)
Subject_ID(外键)

[lswweb]

老大们帮忙呀。。。

[leohuang]

没问题

create table School
(School_ID int identity(1,1) primary key,School_Name varchar(30))


create table Grade
(Grade_ID int identity(1,1) primary key,Grade_Name varchar(30),School_ID int)

create table Subject
(Subject_ID int identity(1,1) primary key,Subject_Name varchar(30),School_ID int)

create table GradeSubject
(GS_ID int identity(1,1) primary key,Grade_ID int,Subject_ID int)



ALTER TABLE Grade ADD CONSTRAINT
FK_Grade_School FOREIGN KEY
(School_ID)
REFERENCES School
(School_ID)

ALTER TABLE Subject ADD CONSTRAINT
FK_Subject_School FOREIGN KEY
(School_ID)
REFERENCES School
(School_ID)

ALTER TABLE GradeSubject ADD CONSTRAINT
FK_GradeSubject_Grade FOREIGN KEY
(Grade_ID)
REFERENCES Grade
(Grade_ID)

ALTER TABLE GradeSubject ADD CONSTRAINT
FK_GradeSubject_Subject FOREIGN KEY
(Subject_ID)
REFERENCES Subject
(Subject_ID)

[昵称被占用了]

把级联删除和级联更新去掉

[zsforever]

顶

[lswweb]

就是需要级联删除与更新呀。。
要不然就不存在问题了。