You're query statements should exactly match the index, so if you have a query that says

... WHERE cCustomer + cInvoice = "ALLAN123456" ...

then you should have a compound index.

>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.