This class produces SQL for JOIN clauses but omits the “single-source” part of the Join grammar:
http://www.sqlite.org/syntaxdiagrams.html#join-source
This visitor is used in Arel::SelectManager#join_sql and is for backwards compatibility with Arel V1.0
# File lib/arel/visitors/join_sql.rb, line 14 def visit_Arel_Nodes_SelectCore o o.source.right.map { |j| visit j }.join ' ' end