The chart below shows how we might distribute the necessary fields among several databases which would supplement the Peach Tree database.  PT Extract reprsents a periodic download of the Peachtree Data; this should not be edited.  All changes should be submitted back to the Peach Tree administrator.  The other databases would be edited directly, and would need to be periodically updated for new members and changes in boat and contact information. 

The yellow row shows the key fields which is the one common tie among the databases, this allows the records to be linked or a process. It is desirable to minimize the redundancy since redundancy in storage will cause redundancy in maintenance tasks.  It probably makes sense to keep last name data as a second common field which is easily recognizable for continuity checks, but it is not unique thus can't serve as the key field.