SQL PostgreSQL 计算行之间的差异
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PostgreSQL calculate difference between rows
提问by user2177232
I tried to calculate difference between rows in a field using a query:
我尝试使用查询计算字段中行之间的差异：
Illustrations:
input:year,month,fixes
output:increase
year | month | fixes | increase
------+-------+----------+-----------
2006 | 04 | 1 | 0
2006 | 05 | 4 | 3
2006 | 06 | 3 | -1
Increase column as output by difference between adjacent rows in fixes.
通过修复中相邻行之间的差异增加列作为输出。
回答by a_horse_with_no_name
This is what window functions are for:
这就是窗口函数的用途：
select year,
month,
fixes,
fixes - lag(fixes) over (order by year, month) as increase,
from the_table;
For more details please see the manual:
http://www.postgresql.org/docs/current/static/tutorial-window.html
有关更多详细信息，请参阅手册：http:
//www.postgresql.org/docs/current/static/tutorial-window.html
