Question

我想知道是否可以在mysql中执行类似的操作：

select 5 as a, 1 as b, a + b as c;

问题是因为我有这个：

CONVERT( SUM(ifnull(commission,0.00)) ,DECIMAL(6,2)) as 'commission',
CONVERT( SUM(ifnull(income,0.00)) ,DECIMAL(6,2)) as 'income',
CONVERT( (SUM(ifnull(income,0.00)) - SUM(ifnull(commission,0.00))) ,DECIMAL(6,2)) as 'profit'

当然，如果不再需要将所有值全部变为SUM，那么第3行会更加优化。

Answer 1

你做不到

select 5 as a, 1 as b, a + b as c;

但你可以做到

select a, b, a + b as c from (select 5 as a, 1 as b) as whatever;

（这是一个嵌套查询，当从外部查询中使用时，它充当假表。）

将这些应用到您的案例中，我们有：

select comission, income, income - comission from (
    select
        CONVERT( SUM(ifnull(commission,0.00)) ,DECIMAL(6,2)) as 'commission',
        CONVERT( SUM(ifnull(income,0.00)) ,DECIMAL(6,2)) as 'income'
    FROM ...
) as t

希望这有帮助。

Answer 2

如果查询没有GROUP BY子句，则可以使用变量 -

SELECT @a:=SUM(1), @b:=SUM(2), @c:=@a + @b FROM table

此外，子查询可以在这里使用。

Answer 3

select a, b, a+b as c 
from ( 
   select 5 as a, 1 as b
) t

从字段求和值（虚拟字段）

3 个答案: