给定以下查询,我如何获得总Amount
发票?Salesperson Code
Customer
SELECT l.[Customer No_], c.[Name], l.[Amount], c.[Salesperson Code], l.[Posting Date]
FROM [Service Invoice Line] l join [Customer] c on
l.[Customer No_] = c.[No_]
Where l.[Posting date] >= '10-01-2012'
and c.[Salesperson Code] > ''
Group by l.[Customer No_],c.[Name],c.[Salesperson Code],l.[Amount],l.[Posting Date]
Order by l.[Customer No_]