Database design - how do I track information over time and query a table for latest data?

Question

We are trying to track our applications in our department and our unit test usage so I have created a database to keep track of this. I have an Applications

Answer 1

Any of these 2 options will work for your scenario:

1 have the logic that adds the new unit test count for the application, insert the record in the history + update the application record's unit test count. Then use a simple select over the application records - history records have nothing to do in this scenario. This is best if you'll have a huge amount of records in the history.

2 use this query against the UnitTestTracking table directly

select application_id, unittestcount from UnitTestTracking u1 
where date_added = ( 
   select max(date_added) from UnitTestTracking u2 
   where u1.application_id = u2.application_id 
)