[英]Simple SQL query with join same table and get value from 2 row in one field
我有一些数据
我需要这样的查询结果:
使用此查询:
select
early.sensor,
early.event,
late.value - early.value as value
from data_table as early
inner join data_table as late on
early.sensor=late.sensor and early.event=late.event
where late.event_date > early.event_date;
我得到这个结果:
假设输入表被称为“ data_table”,并且其中的第四列被称为event_date,则应执行以下操作:
select
early.sensor,
early.event,
late.value - early.value as value
from
data_table as early
inner join data_table as late on
early.sensor=late.sensor
and early.event=late.event
where
late.event_date > early.event_date;
但是,如果有两个以上的值(如@Thorston Kettner所问),那么您将需要一些更复杂的逻辑。
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