如何在子查询结果中查找列的总和？

Question

我必须计算加入表格后得到的一列的总和

SELECT 
  fee_amount 
FROM bill 
  INNER JOIN status 
  ON bill_status_id=status_id 

  INNER JOIN user
  ON bill_user_id =user_id 
WHERE  bill_active='Y'

我必须计算此后返回的fee_amount的SUM，我可以使用下面的一个吗？

SELECT 
  SUM(fee_amount) 
FROM (
  SELECT 
    fee_amount 
  FROM bill 
  INNER JOIN status 
  ON bill_status_id=status_id

  INNER JOIN user
  ON bill_user_id =user_id 
  WHERE  bill_active='Y'
)

请建议。

Answer 1

您不需要使用子查询，只需在第一个查询中添加SUM即可。

SELECT 
  SUM(fee_amount)
FROM bill 
  INNER JOIN status 
  ON bill_status_id=status_id 

  INNER JOIN user
  ON bill_user_id =user_id 
WHERE  bill_active='Y'