如何在MySQL中对多个子查询行进行SUM()? [英] How to SUM() multiple subquery rows in MySQL?

问题描述

问题很简单:我想做:

SELECT SUM((...返回一个带有单个int值的多行的子查询...))AS总计;

SELECT SUM((... a subquery that returns multiple rows with a single int value ...)) AS total;

我该怎么做?我收到一条错误消息，说子查询返回多个行.我需要在子查询中使用它.

How would I do that? I get an error saying that subquery returns more than one row. I need to have it in a subquery.

推荐答案

以下是适合您的方法:

SELECT SUM(column_alias)
FROM (select ... as column_alias from ...) as table_alias

这是一个具体的虚拟示例，展示了实际的方法:

And here's a specific dummy example to show the approach in action:

select sum(int_val) 
from (
  select 1 as int_val 
  union
  select 2 as int_val 
  union 
  select 3 as int_val
) as sub;

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