Column is invalid in select
How I will properly do this: Customer CusID, CusLname, CusFname, CusMname, CusAddress, CusEmailAdd Order OrderID, Order, CusID SQL Select Count(OrderID), o.CusID, CusLname, CusFname, CusMname, CusAddress, CusEmailAdd From Customer c Inner join Order o On c.CusID = o.CusID Group By o.CusID Error Column 'CusLname, CusFname, CusMname, CusAddress, CusEmailAdd' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause. Why do I need to add those columns in the Group By Clause? What will I do to select those columns without having them in the