Just to be clear, with what you are proposing, a multi-base currency exchange table you're potentially looking at 26732 records to maintain (if you set every single combination up). Maybe I'm completely misunderstanding what you're asking for, but I've never heard of or seen an exchange rate table that doesn't use a single base currency for conversions. I mean, other than a minor performance boost in the calculation what would be the purpose? If it were for query-level conversions we could batch calculate and store all the permutations. Maybe that's what you're talking about instead of the user needing to set them up?  Let me know your thoughts and I'll get this cleaned up.