为什么select distinct deptno,last_value(sal) over(order by sal) from emp中distinct去重deptno不起效果?详情如下:
bank=# select distinct deptno,last_value(sal) over(order by deptno) from emp;
deptno | last_value
--------+------------
30 | 3000.00
0 | 5000.00
20 | 2975.00
(3 rows)
bank=# select distinct deptno,last_value(sal) over(order by sal) from emp;
deptno | last_value
--------+------------
30 | 3000.00
20 | 1600.00
0 | 5000.00
30 | 1600.00
20 | 2975.00
20 | 800.00
(6 rows)
bank=# select * from emp;
empno | ename | sal | deptno
-------+-------+---------+--------
3 | feng | 2975.00 | 20
4 | liu | 3000.00 | 30
1 | wang | 800.00 | 20
2 | ren | 1600.00 | 30
5 | yuan | 5000.00 | 0
6 | mu | 1600.00 | 20
(6 rows)