is it possible to do something like that's :

two tables:
 exercice:
   id: int
   name: string..
   category: perhaps string?


  category:
   id: int
   name: string


and I would like for one exercice has many categories, 
doctrine can do that ? or I need to make a new table
for link many category for one exercice.
and search all exercice who have one category to use.