带有postgres窗口函数的重复行

Question

postgres文档(http://www.postgresql.org/docs/9.1/static/tutorial-window.html)讨论了窗口函数.

在他们的例子中:

SELECT salary, sum(salary) OVER (ORDER BY salary) FROM empsalary;

重复处理如下:

 salary |  sum  
--------+-------
   3500 |  3500
   3900 |  7400
   4200 | 11600
   4500 | 16100
   4800 | 25700 <-- notice duplicate rows have the same value
   4800 | 25700 <-- SAME AS ABOVE
   5000 | 30700
   5200 | 41100 <-- same as next line
   5200 | 41100 <--
   6000 | 47100
(10 rows)

你如何做同样的事情,以便重复的行没有给出相同的值？换句话说,我希望这个表看起来如下:

 salary |  sum  
--------+-------
   3500 |  3500
   3900 |  7400
   4200 | 11600
   4500 | 16100
   4800 | 20900 <-- not the same as the next line
   4800 | 25700 <-- 
   5000 | 30700
   5200 | 35900 <-- not the same as the next line
   5200 | 41100 <--
   6000 | 47100
(10 rows)

Answer 1

rows在框架子句中使用in 而不是默认值range

select
    salary,
    sum(salary) over (
        order by salary
        rows unbounded preceding
    )
from empsalary
;
 salary |  sum  
--------+-------
   3500 |  3500
   3900 |  7400
   4200 | 11600
   4500 | 16100
   4800 | 20900
   4800 | 25700
   5000 | 30700
   5200 | 35900
   5200 | 41100
   6000 | 47100

http://www.postgresql.org/docs/current/static/sql-expressions.html#SYNTAX-WINDOW-FUNCTIONS