mysql - 如何从MySQL中的 View 中选择一个字段？

Question

如何在 MySQL 中执行以下查询？

Select SUM(T1.Amount) 
From 
( 
  Select  Distinct PersonName,Amount 
  From  tblusers as T1 
  where city ="xxx"
) 

Answer 1

只是为子查询起个别名:

Select SUM(Amount) 
From (
    Select Distinct PersonName, Amount 
    From  tblusers 
     where city ="xxx")  t

如果您要查找每个人，请添加 GROUP BY:

Select PersonName, SUM(Amount) 
From (
    Select Distinct PersonName, Amount 
    From  tblusers 
     where city ="xxx")  t
Group By PersonName

如果你真的想要每个人的总和(而不是不同的人/金额的总和)，那么你根本不需要子查询:

Select PersonName, SUM(Amount) 
From tblusers 
Where city ="xxx"
Group By PersonName

不过还是要看你的实际需求。