What are the names of the songs they have sung?
select song_name from song where artist_name in  ( SELECT DISTINCT artist_name FROM artist WHERE country   =   "Bangladesh" EXCEPT SELECT DISTINCT artist_name FROM song WHERE rating  >  7 ) 
names of the songs = song_name; sung by artists = FROM artist; condition on artists being from a specific country = WHERE country = 'Bangladesh'; condition excluding those with a rating above a certain value in another table = EXCEPT SELECT DISTINCT artist_name FROM song WHERE rating > 7;