On Sep 3, 2008, at 2:59 PM, [EMAIL PROTECTED] wrote:
>
> I have 1 table (mytable) which is structured somewhat like this:
> id = int (primary key)
> name = varchar()
> type = int
>
> Now all rows with a type, say 1 'constitute' a MyObject. And rows with
> type say 2 are MyOtherObject instances, and so on. So in my
> applications I want to create a class like this:
>
> class MyObject(object):
> def __init__(self, name):
> self.name = name
>
> Then I need to map this to the database. So I write a mapper like
> this:
> myobject_table = select([mytable], mytable.c.type ==
> 1).alias('somealias') (not sure if this is entirely correct. I'm
> writing this post at home and don't have access to my code at the
> office. But this is not the point so...)
> mapper(MyObject, myobject_table)
it is quite common and the pattern you describe is "single table
inheritance". You can map straight to the table and the "type"
column will be taken care of for you. You can configure subtypes
corresponding to each value for "type" and Query for just that
subclass (or for all classes).
http://www.sqlalchemy.org/docs/05/mappers.html#advdatamapping_mapper_inheritance_single
the feature is available in 0.4 and 0.5 but has some improvements to
its behavior in the 0.5 series.
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