On Tuesday, May 6, 2014 9:57:46 AM UTC-7, Ian Whitney wrote:
>
> Hi Jeremy, thanks for the reply.
>
> You're right that many_to_many is probably wrong. I had been working with
> one_to_many, but I couldn't get that to work either. So I was trying
> many_to_many when I wrote my post.
>
> The table I'm working with here stores all previous versions of the row.
> So there will be multiple rows with the same emplid, acad_career,
> stdnt_car_number. But they will have different effective dates and
> effective sequences. (This is PeopleSoft data, btw.)
>
> My eventual goal here is to get the rows with most recent effective date
> and effective sequence. In straight SQL, that ends up looking like this
>
> https://gist.github.com/IanWhitney/7ef1335591466e5b1dcf
>
You can probably do something like:
PsAcadProg.one_to_many(:acad_progs, :class=>PsAcadProg,
:dataset=>proc do |r|
ds = DB[:asr_warehouse__ps_acad_prog].
where(:emplid=>:prog__emplid,
:acad_career=>:prog__acad_career,
:stdnt_car_nbr=>:prog_stdnt_car_nbr)
r.associated_dataset.
from(:asr_warehouse__ps_acad_prog___prog).
where(ds.where{effdt < `sysdate`}.select{max(:effdt)}=>:effdt,
ds.where(:effdt=>:prog__effdt).select{max(:effseq)}=>:effseq)
end)
I didn't test that, but hopefully that or something similar will work.
Thanks,
Jeremy
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