PostgreSQL计算行之间的差异 [英] PostgreSQL calculate difference between rows

问题描述

我尝试使用查询来计算字段中行之间的差异：

I tried to calculate difference between rows in a field using a query:

Illustrations:
input:year,month,fixes
output:increase

     year | month | fixes    | increase
    ------+-------+----------+-----------
     2006 | 04    |       1  | 0
     2006 | 05    |       4  | 3
     2006 | 06    |       3  | -1

通过修订中相邻行之间的差异增加列作为输出。

Increase column as output by difference between adjacent rows in fixes.

推荐答案

这是窗口函数的作用：

select year, 
       month,
       fixes,
       fixes - lag(fixes) over (order by year, month) as increase,
from the_table;

有关更多详细信息，请参见手册：

http://www.postgresql.org/docs/current/static/tutorial-window.html

For more details please see the manual:
http://www.postgresql.org/docs/current/static/tutorial-window.html

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