減法取決於時間SQL

Question

對於每個EVENT_TYPE值被重複不止一次

我需要返回event_type併爲此event_type，註冊的最後一個值的減法SQL語句第二值。我感謝你的幫助

Answer 1

可以使用LEAD()（或LAG()如果你喜歡），以獲得在該系列中的下一個記錄，並計算差值時，纔會有另一條記錄，只有採取每Event_Type最新Time：

With Cte As 
(
    Select *, 
      Row_Number() Over (Partition By Event_Type Order By Time Desc) As Row_Number, 
      Lead(Value) Over (Partition By Event_Type Order By Time Desc) As Prev 
    From YourTable 
) 
Select Event_Type, Value - Prev As Value 
From Cte 
Where Prev Is Not Null 
And  Row_Number = 1 

Answer 2

我會用row_number()和有條件聚集：

select e.event_type, 
     sum(case when seqnum = 1 then value when seqnum = 2 then - value end) as diff 
from (select e.*, 
      row_number() over (partition by e.event_type order by e.time desc) as seqnum 
     from events e 
    ) e 
group by e.event_type 
having count(*) >= 2;