oracle where与having

where与having可以过滤，一般来说尽量使用where ，但是如果过滤条件中有组函数，只能使用having

SQL> select deptno,avg(sal)
  2    from emp
  3    where deptno=10
  4    group by deptno;
 
DEPTNO   AVG(SAL)
------ ----------
    10       2950
 
SQL> 
SQL> select deptno,avg(sal)
  2    from emp
  3    where avg(sal)>2000
  4    group by deptno;
 
select deptno,avg(sal)
  from emp
  where avg(sal)>2000
  group by deptno
 
ORA-00934: 此处不允许使用分组函数
 
SQL> 
SQL> select deptno,avg(sal)
  2    from emp
  3    group by deptno
  4    having avg(sal)>2000;
 
DEPTNO   AVG(SAL)
------ ----------
    20 2258.33333
    10       2950