As for the primary key, Carl and Ed have given you the standard suggestion of using integer primary keys.

As for other indices (I'm not sure whether you are asking in general also), go ahead and have a compound index if it's a common way to look at the data. The index will be used in Rushmore optimization.

>What do you think is best to use in a VFP project when it comes to character indexes or integer indexes? If you use a integer it is very easy to just generate next key. But some times you need a compound index as in browsing items on an invoice. Then I will need a index like Str(invoice_id)+Str(item_id), which is not so easy and fast? to use.