如何在 MySQL 中 SUM() 多个子查询行？
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How to SUM() multiple subquery rows in MySQL?
提问by Tower
The question is simple: I want to do:
问题很简单：我想做：
SELECT SUM((... a subquery that returns multiple rows with a single int value ...)) AS total;
SELECT SUM((...一个子查询，返回多行和一个int值...)) AS total;
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.
我该怎么做？我收到一条错误消息，说子查询返回多于一行。我需要在子查询中使用它。
回答by Ike Walker
Here's an approach that should work for you:
这是一种应该适合您的方法：
SELECT SUM(column_alias)
FROM (select ... as column_alias from ...) as table_alias
And here's a specific dummy example to show the approach in action:
这是一个特定的虚拟示例，用于展示该方法的实际应用：
select sum(int_val)
from (
select 1 as int_val
union
select 2 as int_val
union
select 3 as int_val
) as sub;
回答by jensgram
Couldn't you just do the aggregation withinthe subquery?
你不能只在子查询中进行聚合吗？
SELECT
(SELECT SUM(...) ...) AS total,
...
(Untested!)
（未经测试！）
