>Bottom line: In some cases where there is no other suitable candidate for a primary key, create a new primary key which only use is to identify the record. As shown in the navision database this can be both a surrogate or intelligent key. In other cases where there is a suitable PK available (depends on the domain), use that one (Examples: Invoicenumber, ItemNo, CustomerNo) because it will make you life easier when building, maintaining and debugging your system and keeps performance to the max as it generally needs less joins in queries.

Thanks, Walter.