SQL Server相关查询要取总和

Question

select 
    SUM(Convert(int, (Select SUM(Convert(int, amount)) 
                       from ChargesType 
                       where ChargesType.ID = Charges.ChargesTypeID))) as Amount 
from Charges 
Where Charges.RollNo = 1 

This is my query; I want to get sum of amount column.

Answer 1

Try this instead:

select 
    SUM(t.Amount) as Amount 
from Charges AS c
INNER JOIN
(
   SELECT Convert(int, amount) AS Amount, ID
   FROM  ChargesType
) AS t ON t.ID = c.ChargesTypeID
Where c.RollNo = 1