总不工作

Question

我想从量获得总那里慈善是0减去量的总和，其中慈善是1

SELECT SUM(Amount) - (SELECT SUM(Amount) 
         FROM Transactions 
         WHERE (Charity = 1)) 
    FROM Transactions 
WHERE (Charity = 0) 

该查询运行，但不会给我正确的结果。

Answer 1

治疗为阳性的所有值：

SELECT SUM(ABS(Amount)) - (SELECT SUM(ABS(Amount)) 
         FROM Transactions 
         WHERE (Charity = 1)) 
    FROM Transactions 
WHERE (Charity = 0) 

但它严重怀疑，否定交易应及时治疗与正面相同。如果有，合法，在该表中负的交易，那么他们也许应该被视为底片（在原始查询），或排除：

SELECT SUM(Amount) - (SELECT SUM(Amount) 
         FROM Transactions 
         WHERE (Charity = 1) AND Amount > 0) 
    FROM Transactions 
WHERE (Charity = 0) AND Amount > 0 

不知道什么设施SQLite中可用。在标准SQL中，我可能会改写这个为：

SELECT 
    COALESCE(SUM(CASE WHEN Charity=0 THEN Amount END),0) - 
    COALESCE(SUM(CASE WHEN Charity=1 THEN Amount END),0) 
FROM Transactions 
WHERE 
    Charity in (0,1) AND 
    Amount > 0 

（或类似变换为ABS版）

Answer 2

试试看是否有帮助。

select a.sum1 - b.sum2 
from 
(SELECT SUM(Amount) as sum1 FROM Transactions WHERE (Charity = 0)) A, 
(SELECT SUM(Amount) as sum2 FROM Transactions WHERE (Charity = 1)) B 

Answer 3

尝试下面的（我希望这是SQLite中有效）：

SELECT (SELECT SUM(Amount) FROM Transactions WHERE (Charity = 0)) - 
     (SELECT SUM(Amount) FROM Transactions WHERE (Charity = 1))