Advanced Database Query Exercise

This is an advanced version of the basic Database Query Exercise. You should probably do that one first.

The same instructions apply:

Some tasks can be solved with one single query, other tasks may require a set of queries with human interaction in between. Please point out what to look for in the result set and anything else that should be kept in mind.

If possible explain how the results can be validated.

With the following addition: Make sure that you use the existing indices on large tables such as gameEvents and itemlog.