Summing Up data within different entities

My site contains several games. And each time a user plays a game, i store the game play data in an entity. I have several entities storing different games users have played, So the entity is called gameplay and would have data such as user who played the game, which game was played, date_played, points_gained, etc

And I want to get the sum of all points gained by a specific user. How do i grab that data without having to load all the entities for that user and then adding the points?

Also should i be using something else to store gameplay instead of entities?

 

Thanks in advance for you help

Joshua (elgg newbie)