Please list the top 3 cities with the most number of tweets posted in Canada.
"Canada" is the Country; city with most number of tweets refers to City where Max(Count(TweetID))
SELECT T.City FROM ( SELECT T2.City, COUNT(T1.TweetID) AS num FROM twitter AS T1 INNER JOIN location AS T2 ON T1.LocationID = T2.LocationID WHERE T2.Country = 'Canada' GROUP BY T2.City ) T ORDER BY T.num DESC LIMIT 3
database name:db_id social_media
location table location Cols: location id dtype integer, Country dtype text, State dtype text, state code dtype text, City dtype text, 
user table user Cols: user id dtype text, Gender dtype text, 
twitter table twitter Cols: tweet id dtype text, Weekday dtype text, Hour dtype integer, Day dtype integer, language dtype text, is reshare dtype text, Reach dtype integer, retweet count dtype integer, Likes dtype integer, Klout dtype integer, Sentiment dtype real, text dtype text, location id dtype integer, user id dtype text, 
