부서 이름이 'OPERATIONS' 인 부서 소속 사원을 모두 삭제하려면?

1. 1DELETE FROM emp WHERE deptno IN (SELECT deptno FROM dept WHERE dname = 'OPERATIONS')
2. 2DELETE emp JOIN dept ON emp.deptno=dept.deptno WHERE dname = 'OPERATIONS'
3. 3DELETE FROM emp e, dept d WHERE e.deptno = d.deptno AND d.dname = 'OPERATIONS'
4. 4DELETE emp.* FROM emp, dept WHERE dname = 'OPERATIONS'