Game
{
    int id;
    User player
    Collection<Round> round
    ...
}

Round
{
   int id;
   ...
}
User
{
   int id;
   ...
}

"SELECT g FROM Game JOIN  g.player AS p where p.id = "+user.getId()

"SELECT r FROM Round JOIN Game AS g WHERE g.rounds = r JOIN User AS p WHERE p.id = "+user.getId()