SUM of values of a column from several records

Dear Akshit, 

Everything seems to be correct with the code itself. I tried a very similar code with the OOB tables and it returned correct result: 

public void Execute(UserConnection userConnection)
        {
            var result = "";
            var sel = new Select(userConnection)
                    .Column(Func.Sum("Order", "Amount")).As("OrderAmount")
                .From("Order")
                .Where("AccountId").IsEqual(new Select(userConnection)
                                                .Column("Id")
                                                .From("Account")
                                                .Where("Name").IsEqual(Column.Parameter("Accom (sample)")))
                                   .And("StatusId").IsNotEqual(new Select(userConnection)
                                                .Column("Id")
                                                .From("OrderStatus")
                                                .Where("Name").IsEqual(Column.Parameter("2. Confirmation")))
                 as Select;
            result = sel.ExecuteScalar<int>().ToString();
            Console.WriteLine(result);
        }

You get 0 most likely because no records match the filter. Please run this query in SQL (SQL executor if your instance is in the cloud) and check what result you get.  

Best regards, 

Dennis