title: Doctrine of SQL get state from log table
body: <p>I can't come up with how to retrieve certain data from my sql.
  I am working with symfony3 and doctrine. But an SQL will do too.</p>
  
  <pre><code>Game
  - id
  - hometeam
  - awayteam
  
  Player
  - id
  - team
  
  GameAction
  - id
  - game
  - player
  - action
  
  Action
  - id
  - name
  </code></pre>
  
  <p>2 of the Actions in the Actions-Table are 'gets on ice' and 'gets off ice'</p>
  
  <p>I want to find out which players are currently 'on ice'. I am looking for all those players which had an 'gets on ice'-event with no following 'gets off ice' event in this game.</p>
  
  <p>How would such a query look like? </p>
  
  <p>Any hint much appreciated</p>