差總在同一列

Question

我有此列，

ID Year ColumnDesc Amount 
    1 2000 Taken  100 
    1 2000 NotTaken 10 
    1 2001 Taken  200 
    1 2001 NotTaken 100 

，所以我需要做同樣的ID和新年，所以我的表應該像金額的差額。

ID Year ColumnDesc Amount 
    1 2000 Taken 90 
    1 2001 Taken 100 

任何一個可以幫助我..

Answer 1

我想你想要有條件聚集：

select id, year, 'Taken' as ColumnDesc, 
     sum(case when ColumnDesc = 'Taken' then Amount 
       when ColumnDesc = 'Not Taken' then - Amount 
       else 0 
      end) as Amount 
from t 
group by id, year;