Database: social_media
Question: Please list the top 3 cities with the most number of tweets posted in Canada.
SQL: 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