Question: Find all the songs that do not have a back vocal.
Schema: create table songs (title varchar, songid varchar, PRIMARY KEY (title)); create table vocals (songid varchar, PRIMARY KEY (songid))
SQL: select distinct title from vocals as t1 join songs as t2 on t1.songid = t2.songid except select t2.title from vocals as t1 join songs as t2 on t1.songid = t2.songid where type = "back"