18:48 <karamorf> I'm new to using datamapper and trying to figure out exactly how to do a subquery. The results I want are found with this SQL: "select id from sap_users where personnel_number not in (select supervisor from sap_users);" but for the life of me I can't figure out how to do it when using the objects. If someone has a good link for how to do subquerries that would work great as well, I'm just not being very succesful with my googling :)

18:51 <postmodern> karamorf, sounds like you want to define two models that map to sap_users

18:52 <postmodern> karamorf, one a normal User and the other a Supervisor

18:52 <postmodern> Then maybe to Users.all - Supervisors.all

18:52 <postmodern> *do

19:52 <karamorf> postmodern, that sounds good. so it looks like the common way to do this would be to use a Discremenator property. However I don't know who the supervisor are upfront, I'd have to loop over the set of data after populating the Users object to set them as Supervisors. I'd also like Supervisors to still be in the Users class.

19:53 <karamorf> is there some way I can set the supervisors object to select the rows the have personnel_number matching the supervsior?

19:54 <postmodern> maybe you want a self-referential relationship

19:56 <karamorf> oo, that looks like a good path to go down. Thanks, I'll do some reading.

19:57 <postmodern> belongs_to :supervisor, model: 'User', child_key: ...