arel_multiple_cte.rb

# from_cte_sql = ::Namespace::From.where_clause
# ..


from_table = Arel::Table.new(:from_lane)
to_table = Arel::Table.new(:to_lane)
rates_table = Arel::Table.new(:rates)

rates_table
  .join(from_table).on(rates_table[:from_id].eq(from_table[:id]))
  .join(to_table).on(rates_table[:to_id].eq(to_table[:id]))
  .project(rates_table[Arel.star])
  .with([
          Arel::Nodes::As.new(from_table,
                              Arel::Nodes::SqlLiteral.new("(#{from_cte_sql.to_sql})")),
          Arel::Nodes::As.new(to_table,
                              Arel::Nodes::SqlLiteral.new("(#{to_cte_sql.to_sql})")),
          Arel::Nodes::As.new(rates_table,
                              Arel::Nodes::SqlLiteral.new("(#{rate_cte_sql.to_sql})"))])