I have a following situation:
Table buyers has 8 rating columns (AAA,AA,A,NR,B,C,No Rating) which are determining different interest rates for each rating value. Each buyer has different interest rates in these rating columns.
Table invoices has lookup field which looks up from a supplier table the rating of the supplier and adds that to the supplier_rating field.
Now I want to get the correct interest rate from the buyer table based on the rating value of the supplier into invoices table.
How should I do this?