php - Using Indexes in mysql correctly -

i know how can make proper indexed table, understand concept using movies example:

i have these 5 tables multiple fields list here these tables primary indexes fields only:

movies   movie_id = primary index actors   actor_id = primary index geners   gener_id = primary index reviews   review_id = primary index 

and have these tables relation 2 columns each, unsure type of indexes should have these relational tables:

movie_actor    movie_id,actor_id movie_gener    movie_id,gener_id movie_review    movie_id,review_id 

i have join on these fields if wants 1 movie details use such query:

select *  movies m left join movie_actor  ma  on ma.movie_id = m.movie_id left join actors         on a.ator_id   = ma.actor_id left join movie_gener  mg  on mg.movie_id = m.movie_id left join geners       g   on g.gener_id  = mg.gener_id left join movie_review mr  on mr.movie_id = m.movie_id left join reviews      r   on r.review_id = mr.review_id  m.movie_id = 1234 

so kind of index should use on relational tables (movie_actor,movie_gener,movie_review) both fields, primary on 1 or index on both? thanks

only 1 field can primary key on each table table can have 1 primary key (corrected user). @ post information differences between index, primary, unique, fulltext in mysql?