what is the video game rating whose rating system includes the content descriptor of violence?
Entity Entity Entity Entity Entity Entity Entity Entity
m.042zl8b m.042zl98 m.042zl8x m.042zl9n m.042zl92 m.042zl8q m.042zl9g m.042zl8j
Everyone Mature Everyone 10+ Rating Pending Adults Only Teen Kids to Adults Early Childhood
class class entity
cvg.computer_game_rating cvg.computer_game_rating_system m.042zlwf
cvg.computer_game_rating cvg.computer_game_rating_system cvg.computer_game_content_descriptor
Video Game Rating Video Game Rating System Violence
none none none
cvg.computer_game_rating.rating_system cvg.computer_game_rating_system.content_descriptors
Rating system Content descriptors
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> PREFIX : <http://rdf.freebase.com/ns/> 
SELECT (?x0 AS ?value) WHERE {
SELECT DISTINCT ?x0  WHERE { 
?x0 :type.object.type :cvg.computer_game_rating . 
?x1 :type.object.type :cvg.computer_game_rating_system . 
VALUES ?x2 { :m.042zlwf } 
?x0 :cvg.computer_game_rating.rating_system ?x1 . 
?x1 :cvg.computer_game_rating_system.content_descriptors ?x2 . 
FILTER ( ?x0 != ?x1 && ?x0 != ?x2 && ?x1 != ?x2  )
}
}
(AND cvg.computer_game_rating (JOIN cvg.computer_game_rating.rating_system (JOIN cvg.computer_game_rating_system.content_descriptors m.042zlwf)))