我有一张桌子:
Number | Event | Weight
1 4 150
1 4 160
2 5 200
2 4 200
3 6 190
3 6 195
对于每一行,我想从它的Weight
中减去另一行的Weight
,其中Number
和Event
匹配(如果存在)。所需的输出是:
Number | Event | Weight | DIFF
1 4 150 -10
1 4 160 10
2 5 200 NULL
2 4 200 NULL
3 6 190 -5
3 6 195 5
这样的手术可能吗?不确定是否相关,最终我需要将此查询转换为view
。提前致谢。
你需要一个左连接:
select
t.*,
t.weight - tt.weight diff
from tablename t left join tablename tt
on tt.number = t.number and tt.event = t.event and tt.weight <> t.weight
可以通过简单地减去连接表中的列来完成。当其中一个操作数为null时,算术运算的结果为null:
select a.Number, a.Event, a.Weight, a.Weight - b.Weight as DIFF
from a
left join b on a.Number = b.Number and a.Event = b.Event