Project Outline: SQL server 6.5; Database has about ten tables;
Five of these tables are logically depend on 3 fields.
Very important: the database is to be updated automatically
on hourly basis. Information is being parsed from flat files.
This information includes all three "key" fields (along with other info fields).

Database relationship can be designed "straight" having three keys
defined as a compound PK and repeated on all five tables.

As an alternative, a four-fields table can be created. One field can be defined
as a PK with Autonumber format to serve as a "Physical Key";
three other fields will be included with the Unique constrain.
Then, a the single Physical Key with a Number format will reference each of five tables.
In this case, in order to maintain a database integrity, a Trigger has to be created.
The purpose of the trigger is:
before update of any of five tables
1)find-out a right physical key for the table to be updated
2)insert this physical PK.
The trigger should be fired every time the database has to be updated.

Question: what is a right design decision?