CREATE TABLE [dbo].[stu](sno INT UNIQUE)
CREATE TABLE dbo.sjb(sno INT CONSTRAINT sno_fk REFERENCES dbo.[stu](sno) ON DELETE CASCADE )

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SQL code
create table B(B_id,
 A_id int foreign key(A_id) references A(A_id) ON DELETE CASCADE)

------解决方案--------------------
SQL code

on delete cascade

------解决方案--------------------
探讨


SQL code
create table B(B_id,
 A_id int foreign key(A_id) references A(A_id) ON DELETE CASCADE)


------解决方案--------------------
级联删除。