Question

I understand an intermediate class is often introduced to capture information in a situation where for example, a team has many players, and a player plays for many teams over the years. The intermediate class introduced is contract with cardinality as shown:

Team -1—-N- Contract -N—-1- Player

Let’s say however that 98% of all queries only want current information and don’t care about historical information. Given the name of a player, they want to know information about his current team, and perhaps current contract.

Given the above relationship, should all the contracts always be looked through to find the current one first, and then from there access information about the team? Or should an optimization be made with direct linkage between the player and his current team?

Thanks

Answer 1

If it is assured that there is only one team for each player at given time, you just add
currentTeam column to the Player table and that’s it. But remember you must update it every time you update the Contracts table! And it must be done within the transaction, so that the database is kept consistent at any time.

You violate some normal form this way, but you know what and why you are doing that – for efficiency and optimization. I do this trick many times.