SQL 删除被其他表参照的记录

create table dept_accidents
( deptno         integer,
  accident_name varchar(20) )
　
insert into dept_accidents values (10,'BROKEN FOOT')
insert into dept_accidents values (10,'FLESH WOUND')
insert into dept_accidents values (20,'FIRE')
insert into dept_accidents values (20,'FIRE')
insert into dept_accidents values (20,'FLOOD')
insert into dept_accidents values (30,'BRUISED GLUTE')
　
select * from dept_accidents
　
    DEPTNO ACCIDENT_NAME
---------- --------------------
        10 BROKEN FOOT
        10 FLESH WOUND
        20 FIRE
        20 FIRE
        20 FLOOD
        30 BRUISED GLUTE

1 delete from emp
2  where deptno in ( select deptno
3                      from dept_accidents
4                     group by deptno
5                    having count(*) >= 3 )

select deptno
  from dept_accidents
 group by deptno
having count(*) >= 3
　
    DEPTNO
----------
         20