Find the average number of downloads for Single-Tables released by '2Pac' between 2001 and 2013.
2Pac is an artist; releaseType = 'single'; between 2001 and 2013 refers to groupYear between 2001 and 2013; average number of downloads = AVG(totalSnatched);
SELECT AVG(totalSnatched) FROM torrents WHERE artist LIKE '2Pac' AND releaseType LIKE 'Single' AND groupYear BETWEEN 2001 AND 2013
database name:db_id music_tracker
torrents table torrents Cols: groupName dtype text, totalSnatched dtype integer, artist dtype text, groupYear dtype integer, releaseType dtype text, groupId dtype integer, id dtype integer, 
tags table tags Cols: index dtype integer, id dtype integer, tag dtype text, 
