CREATE TABLE torrents (groupname TEXT, totalsnatched DECIMAL, artist TEXT, groupyear DECIMAL, releasetype TEXT, groupid DECIMAL, id DECIMAL)
CREATE TABLE tags (index DECIMAL, id DECIMAL, tag TEXT)

What are the artist/groups that released only one CD?
SELECT artist FROM torrents GROUP BY artist HAVING COUNT(*) = 1
SELECT "artist" FROM "torrents" GROUP BY "artist" HAVING COUNT(*) = 1