IF (EXISTS(Select * from sys.sysprocedure where LCase(proc_name) = LCase('CalcSaleInvoiceTotalNoVat')))
THEN Drop procedure CalcSaleInvoiceTotalNoVat
END IF

GO

create function DBA.CalcSaleInvoiceTotalNoVat( in @InvoiceNo integer ) 
returns numeric(12,4)
begin
  declare @res numeric(12,4);
  set @res = (select round(SUM(A.Qty*(SL.SellPrice/(1+SL.VatRate)*(1+Sl.Discount/100))),2)
      from SaleOrderLines_Articles as SA join SaleOrderLines as SL on SA.SaleLineID = SL.ID
        join Articles as A on A.InvoiceNo = SA.InvoiceNo and A.ArticleNo = SA.ArticleNo
      where SA.InvoiceNo = @InvoiceNo);
  return(@res)
end