11일차 # 9-27: FOREIGN KEY constraints

 * ON DELETE CASCADE

delete from d1

where deptno = 30;

==> 오류: ORA-02292: 무결성 제약조건(MVP20.E1_DEPTNO_FK)이 위배되었습니다- 자식 레코드가 발견되었습니다

alter table e1

drop constraint e1_deptno_fk;

alter table e1

modify (deptno constraint e1_deptno_fk references d1(deptno)

on delete cascade);

delete from d1

where deptno = 30;

select * from d1;

select * from d2;

  * ON DELETE SET NULL

delete from d2

where deptno = 30;

==> 오류: ORA-02292: 무결성 제약조건(MVP20.E2_DEPTNO_FK)이 위배되었습니다- 자식 레코드가 발견되었습니다

alter table e2

drop constraint e2_deptno_fk;

alter table e2

modify (deptno constraint e2_deptno_fk references d2(deptno)

on delete set null);

delete from d2

where deptno = 30;

select * from d2;

select * from e2;