Mysql 在嵌套SQL中，如何按值对分组求和

我有以下SQL

SELECT MAX(o.tax) as tax_value 
FROM offer AS o 
WHERE o.status in (1) 
GROUP BY(o.offer_no)

假设上面的查询返回3条记录，但我想在另一个SQL中求这些记录的总和

比方说

SELECT SUM(SELECT MAX(o.tax) as tax_value 
FROM offer AS o 
WHERE o.status in (1) 
GROUP BY(o.offer_no))  as created

---

但这给了我一个错误信息。我怎样才能解决这个问题。我想得到这些值的总和。

您可以使用表表达式：

select sum(x.tax_value) as tax_value
from ( -- table expression here acts as a table
  SELECT MAX(o.tax) as tax_value 
  FROM offer AS o 
  WHERE o.status in (1) 
  GROUP BY(o.offer_no)
) x

将其放入子查询：

SELECT SUM(tax_value)
FROM (
    SELECT MAX(tax) AS tax_value
    FROM offer
    WHERE status = 1
    GROUP BY offer_no) x

---

是的，现在可以用了。我还有一个问题，如何在一个SELECT语句中求和这些值，而不嵌套在SELECT中。你不能。查询中只能有一个聚合级别。