...查询部门平均工资,平且显示工资等级,按部门分组,sql语句怎么写...答:select t1.deptno, t1.dname, t1.avgsal, max(case when t1.avgsal between t2.losal and t2.hisal then t2.grade end) grade from (select a.deptno, b.dname, round(avg(a.sal), 2) avgsal from emp a, dept b where a.deptno = b.deptno group by...