Daniel Nogradi, el 12 de junio a las 14:41 me escribiste:
> > > > > > > sqlobject.dberrors.OperationalError: no such column:
> > > > > > > animal.cage_id
> > > > > >
> > > > > > But there is "cage_id" columnm in the "animal" table
> > > > >
> > > > > Well, that's exactly the problem :)
> > > >
> > > > Are you sure this part of the problem is in SQLObject and not in
> > SQLite?
> > > > (There are probably other problems - inheritance was developed for
> > simple
> > > > use cases and hardly support joins and aggregates...)
> > >
> > > I only guess that the problem is with SQLObject since SQLite itself is
> > > pretty reliable. But I'm getting also more and more convinced that
> > > using inheritance is not a good idea, I ran into other similar
> > > troubles too. So probably it's best to stay away from them.
> >
> > I use inheritance a lot, but I don't usually do JOINs (I just do it the OO
> > way since I don't have very large sets of data) and it works very well.
>
>
> Hi, can you please test the code below (if you have sqlite)? If you
> use a different db, can you please change the connectionForURI to use
> yours and test then? The correct output should be 5 of course.
I can't, but I don't see the point. What do you expect me to see running
the test?
> If you don't use joins, how would you select the total number of
> animals in a zoo in this example? Select (almost) everything and
> filter through them in python?
For counting:
count = 0
for c in the_zoo.cages:
count += len(c.animals)
or:
count = 0
for a in animal.select():
if a.cage.zoo == the_zoo:
count += 1
For selecting:
my_list = [a for a in animal.select() if predicate(a)]
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