总和未显示正确结果

Question

我有三个名为EasyPaisa，TimePay和Omni的表，其中Profit字段为EasyPasia (10,10)，Omni得到(15,15)，TimePay获得(20,20)。

1. EasyPaisa总和利润20
2. Omni，总和利润30
3. TimePay，总和利润40

当我通过此查询获取利润时：

SELECT 
    Sum(EasyPaisa.Profit) AS Expr1, 
    Sum(Omni.Profit) AS Expr2, 
    Sum(TimePay.Profit) AS Expr3
FROM 
    EasyPaisa, 
    Omni, 
    TimePay;

它给我的结果加倍实际结果

1. EasyPaisa利润为40
2. Omni Profit as 60
3. TimePay利润为80

Answer 1

你在找这个吗？

SELECT 
  (SELECT SUM(Profit) FROM EasyPaisa) Expr1,
  (SELECT SUM(Profit) FROM Omni)      Expr2, 
  (SELECT SUM(Profit) FROM TimePay)   Expr3

输出：

| EXPR1 | EXPR2 | EXPR3 |
-------------------------
|    20 |    30 |    40 |

这是 SQLFiddle 演示。