Your query works for me in v3.2.7 (you didn't say what version you're using). Can you produce a transcript from the SQLite shell, similar to below, showing the failure?
sqlite> select * from tItem; id dataID x ---------- ---------- ---------- 1 1 a 2 <> b 3 2 c 4 3 d 5 <> e 6 <> f sqlite> select * from tMap; childID parentID ---------- ---------- 2 1 3 1 5 4 sqlite> select * from tData; id size data ---------- ---------- ---------- 1 3 abc 2 4 abcd 3 5 abcde sqlite> select i.id, i.x, d.size ...> from tItem i left join tData d on i.dataID = d.id ...> join tMap m on i.id = m.childID and m.parentID = 1; id x size ---------- ---------- ---------- 2 b <> 3 c 4 Regards