On Tuesday, May 3, 2016 at 8:13:00 AM UTC-7, The Bang Nguyen wrote:
>
> Hi Jeremy,
>
> I did figure out the SQL query to achieve my need.
> However, as a newbie to Sequel, I do not know how to turn it into a Sequel
> DSL though
>
> Below is my SQL query:
> ```
> select models.id
> ,case
> when (select max(events.created_at) from events where
> event_type='DoSomething' and models.id = events.model_id) is not null
> and
> (select max(events.created_at) from events where
> event_type='UndoSomething' and models.id = events.model_id) is null
> then true
> when (select max(events.created_at) from events where
> event_type='DoSomething' and models.id = events.model_id)
> >
> (select max(events.created_at) from events where
> event_type='UndoSomething' and models.id = events.model_id)
> then true
> else false
> end as did_something
> from models;
> ```
>
I think something like this will work:
class Model < Sequel::Model
dataset_module do
def with_did_something
ds =
db[:events].where(:models__id=>:events__model_id).select{max(:events__created_at)}
do_ds = ds.where(:event_type=>'DoSomething')
undo_ds = ds.where(:event_type=>'UndoSomething')
select_append(Sequel.case(
{Sequel.~(do_ds=>nil) & {undo_ds=>nil} => true,
do_ds > undo_ds => true},
false
).as(:did_something))
end
end
end
Thanks,
Jeremy
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