AVB (8/25/2013)
At some point 95% of shipments and invoices will move into a final status (Paid, Shipment Delivered) so I would think indexes wouldn't be useful.
If you frequently query for non-final statuses, those indexes will potentially be very useful indeed.
p.s. Have you tested and confirmed that the time required for the join is noticeable and unacceptable?
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability