Error while using Aggregate function(sum) with joins in sqlserver

[Jagdeep singh]

There are 2 tables

1.customers
2.quotations

Here I fill my datagridview with this query

SELECT   quotations.CustomerKey as Id
       , customers.Name
       , SUM(quotations.AmountDue) as AmountDue
FROM     customers
         INNER JOIN
         quotations
  ON     customers.CustomerKey=quotations.CustomerKey
GROUP BY quotations.CustomerKey

while using agrregate function with joins , This Error Came

Column 'customers.Name' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause

If i run this query without aggregate function then the result came, i think some changes are requied ... So pls help me on this

[NeoPa]

You're mistaken (at least what you state as true is not so). That error is there when the GROUP BY clause is there, and not when the SUM() call is there necessarily.

The reason is that you have referred to a field in the SELECT clause of a GROUP BY query without either being true of :

1. The field is listed in the GROUP BY clause.
2. The field is referenced within an aggregate function.

As neither of these is true then it cannot possibly make sense so the SQL engine tries to tell you where you've gone wrong.