Re: [sqlobject] [SQLObject] Table Joining to Itself

[Victor Ng <vn...@sy...>]

Similiarly - if you wanted to have Many to Many relationships, you can 
use:

parents = RelatedJoin('prodcats',
                         addRemoveName='Parent',
                         intermediateTable='prodcats_parent_child',
                         otherColumn = 'parent_id',
                         joinColumn='child_id')

children = RelatedJoin('prodcats',
                         addRemoveName='Child',
                         intermediateTable='prodcats_parent_child',
                         otherColumn= 'child_id',
                         joinColumn='parent_id')

Just remember to use ifNotExists when you create the table - since you 
run the risk of creating the intermediateTable twice.

prodcats.createTable(ifNotExists = True)

vic

On Mar 24, 2004, at 9:20 AM, David McNab wrote:

> Hi,
>
> I'm posting here in the hope that my problem, and its solution, might 
> save others from the battle I've had.
>
> Basically, I'm implementing a web shopping cart. While I was tempted 
> to have just a plain 2 or 3 level product hierarchy, this felt too 
> restrictive and I wanted a more general solution - the ability to have 
> an unrestricted n-level hierarchy of product categories.
>
> After some experimenting and reading SQLObject source, the following 
> solution came out:
>
>   class prodcats(SQLObject):
>       _connection = _conn
>       name=StringCol()
>       longname=StringCol()
>       parent=ForeignKey('prodcats', default=None)
>       children=MultipleJoin('prodcats', joinColumn='parent_id')
>
>   prodcats.createTable()
>
>   rPets = prodcats.new(
>     name='pets', longname='Pets')
>
>   rBirds = prodcats.new(
>     name='birds', longname='Birds', parent=rPets)
>
>   rLargeBirds = prodcats.new(
>     name='large', longname='Large Birds', parent=rBirds)
>
>   rSmallBirds = prodcats.new(
>     name='small', longname='Small Birds', parent=rBirds)
>
>   rDogs = prodcats.new(
>     name='dogs', longname='Dogs', parent=rPets)
>
>   rLargeDogs = prodcats.new(
>     name='large', longname='Large Dogs', parent=rDogs)
>
>   rSmallDogs = prodcats.new(
>     name='small', longname='Small Dogs', parent=rDogs)
>
> -- 
>
> Kind regards
> David
>
> --
>
>
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