I doubt you'll see any difference for two keys but it maybe faster for bigger # of keys. Anyway, I wouldn't worry about that until your original query became slow. :)

>Sergey,
>
>I wonder if it is worthwhile to combine the two fields in the expression (as in Craig's example).
>
>>In this case you don't need compound index because you're using each field separately in your WHERE condition.
>>
>>>Is there a benefit in terms of Rushmore in creating compound indices for free tables?
>>>
>>>For example, when we extract invoice headers, part of the SQL statement might contain "where cCustomer = 'ALLAN' and cInvoiceNo = '123456'".
>>>Should there be an index on 'cCustomer + cInvoiceNo' as well as 'cCustomer' and 'cInvoicNo'?
>>>
>>>TIA.