我怎样才能得到三个函数在不同的状态

Question

我有一个product表，我想要得到数量的总和一个领域是不同的状态

这里是我的表...

kind| qty 
1 | 150 
8 | 122 
1 | 177 
3 | 60 
8 | 66 
... 

如何我能得到这个说法

select sum(qty) when kind=1, sum(qty) when kind=8, sum(qty) when kind=3, 
sum1+sum2-sum3 from mytable 

最后一行我想从这句话得到我的SQL计算领域

sum1+sum2-sum3 from mytable 

，其结果将是

sum1 , sum2, sum3, calc 

Answer 1

可以按如下方式做到这一点：

SELECT 
sum(CASE kind WHEN 1 THEN qty ELSE 0 END) kind1, 
sum(CASE kind WHEN 0 THEN qty ELSE 0 END) kind8, 
sum(CASE kind WHEN 3 THEN qty ELSE 0 END) kind3, 
sum(CASE kind WHEN 1 THEN qty ELSE 0 END) 
+ sum(CASE kind WHEN 0 THEN qty ELSE 0 END) 
+ sum(CASE kind WHEN 3 THEN qty ELSE 0 END) Total, 
FROM 
    mytable 

Answer 2

select 
    sum(case when kind in (1) then qty else 0 end) as sum1, 
    sum(case when kind in (8) then qty else 0 end) as sum2, 
    sum(case when kind in (3) then qty else 0 end) as sum3, 
    sum(case when kind in (1, 8) then qty else -qty end) as calc 
from mytable 
where kind in (1, 3, 8) 

Answer 3

SELECT kind1, kind8, kind3, (kind1 + kind8 - kind3) totalResult 
FROM 
(
    SELECT SUM(CASE WHEN kind = 1 THEN qty ELSE 0 END) kind1, 
      SUM(CASE WHEN kind = 8 THEN qty ELSE 0 END) kind8, 
      SUM(CASE WHEN kind = 3 THEN qty ELSE 0 END) kind3 
    FROM tableName 
) x 

SQLFiddle Demo