oracle 조인으로 삭제하기

DELETE FROM EMP A
 WHERE EXISTS (
        SELECT 1
          FROM DEPT B
         WHERE A.DEPTNO = B.DEPTNO
           AND B.DEPTNO = '20'
        );

DELETE FROM EMP A
 WHERE A.DEPTNO =  (
        SELECT B.DEPTNO
          FROM DEPT B
         WHERE A.DEPTNO = B.DEPTNO
           AND B.DEPTNO = '20'
        );
        
DELETE FROM EMP A
 WHERE (A.DEPTNO, A.ENAME) =  (
        SELECT B.DEPTNO, B.NAME
          FROM DEPT B
         WHERE B.DEPTNO = '20'
        );