joining and array with a table in ActiveRecord


I am pretty new to Ruby on Rails and I have no idea how to solve the

I have a join query on a table like this:

  def mytags
    Taggable.joins("JOIN taggables as filter ON taggables.tag_id =
filter.tag_id WHERE filter.taggable_type = 'User' AND filter.taggable_id
= 1").all

this works perfectly fine.
then I want to join the result on another table, where
OtherTable.joins(@mytags) works also fine BUT I want to
join on two other colums and NOT on the ids....

Can anyone tell me how to do this?