-- Database schema
| torrents : groupName [ TEXT ] , totalSnatched [ INTEGER ] , artist [ TEXT ] , groupYear [ INTEGER ] , releaseType [ TEXT ] , groupId [ INTEGER ] , id [ INTEGER ] primary_key | tags : index [ INTEGER ] primary_key , id [ INTEGER ] , tag [ TEXT ] |
-- -- An American rapper '2Pac' released his first solo album in 1991, how many years have passed until his next album was released?

SELECT ( SELECT groupYear FROM torrents WHERE artist LIKE '2Pac' AND releaseType LIKE 'album' ORDER BY groupYear LIMIT 1, 1 ) - groupYear FROM torrents WHERE artist LIKE '2Pac' AND releaseType LIKE 'album' AND groupYear = 1991;