I wrote RFC: DBIx::Iterator because I needed to join over 20 tables in a database, but the schema was unknown...no one was quite sure how the tables were supposed to be joined exactly. So I did a lot of experimenting with joining and unjoining tables. In a normal SQL statement though, if you want to remove the table in a join, you have to remove the appropriate SELECT columns, the table in the FROM clause, and the appropriate parts of the WHERE clause. With the iterators I used, I could remove a join by commenting out one line (saving lots of time in the "experimenting" phase). So in a way, it was over 20 iterators joined together (though all the same type).