Arel 3.0.3 Visitor for MSSQL UPDATE with JOIN monkey patch

arel_mssql_join_visitor_for_update_statement.rb

module Arel
  module Visitors
    class MSSQL
      private

      def visit_Arel_Nodes_UpdateStatement o
        if o.orders.empty? && o.limit.nil?
          wheres = o.wheres
        else
          key = o.key
          unless key
            warn(<<-eowarn) if $VERBOSE
(#{caller.first}) Using UpdateManager without setting UpdateManager#key is
deprecated and support will be removed in ARel 4.0.0.  Please set the primary
key on UpdateManager using UpdateManager#key=
            eowarn
            key = o.relation.primary_key
          end

          wheres = [Nodes::In.new(key, [build_subselect(key, o)])]
        end

        [
          "UPDATE #{visit(o.relation.respond_to?(:left) ? o.relation.left : o.relation)}",
          ("SET #{o.values.map { |value| visit value }.join ', '}" unless o.values.empty?),
          "FROM #{visit o.relation}",
          ("WHERE #{wheres.map { |x| visit x }.join ' AND '}" unless wheres.empty?),
        ].compact.join ' '
      end
    end
  end
end

This overloads Arel::Visitors::ToSql method of the same name, which Arel::Visitors::MSSQL is a descendant of.