delete the highest earning employees in each department

SQL> select * from dept order by deptno;

DEPTNO DNAME LOC
---------- -------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON


SQL> select empno,ename,job,sal,deptno from emp;

EMPNO ENAME JOB SAL DEPTNO
---------- ---------- --------- ---------- ----------
7369 SMITH CLERK 800 20
7499 ALLEN SALESMAN 1600 30
7521 WARD SALESMAN 1250 30
7566 JONES MANAGER 2975 20
7654 MARTIN SALESMAN 1250 30
7698 BLAKE MANAGER 2850 30
7782 CLARK MANAGER 2450 10
7788 SCOTT ANALYST 3000 20
7839 KING PRESIDENT 5000 10
7844 TURNER SALESMAN 1500 30
7876 ADAMS CLERK 1100 20
7900 JAMES CLERK 950 30
7902 FORD ANALYST 3000 20
7934 MILLER CLERK 1300 10

14 rows selected.
SQL> delete from emp a where
a.sal = (select max(sal) from emp b
where a.deptno = b.deptno);

4 rows deleted.

SQL> select ename, sal, deptno from emp
order by deptno, ename;

ENAME SAL DEPTNO
---------- ---------- ----------
CLARK 2916.67 10
MILLER 2916.67 10
ADAMS 2175 20
JONES 2975 20
SMITH 2175 20
ALLEN 1600 30
JAMES 1566.67 30
MARTIN 1566.67 30
TURNER 1566.67 30
WARD 1566.67 30