On May 5, 2008, at 5:11 PM, Matt Haggard wrote:
>
> I've got a kind of goofy schema, and I'm trying to map it. I've got
> Questionnaire types, Sections and Questions all joined in a single
> association table:
>
> join_table : type_id | section_id | question_id
> questions_table : id | question_text
> sections_table : id | section_name
> types_table : id | type_name
>
> So, a single question can appear in different sections for different
> types. How do I do the mapping? This is what I've got, and it
> doesn't work.
>
> mapper(Question, questions_table)
> mapper(Section, sections_table, properties={
> 'questions':relation(Question, backref='section',
> secondary=join_table)
> })
> mapper(QType, types_table, properties={
> 'sections':relation(Section,
> backref = 'type',
> secondary = join_table
> primaryjoin = types_table.c.id==join_table.c.type_id,
> secondaryjoin = join_table.c.section_id==sections_table.id
> )
> })
your table is not a many-to-many table, its just another entity table
with associations to other entities. "secondary" is not the
appropriate construct in this case; use an association mapping :
http://www.sqlalchemy.org/docs/04/mappers.html#advdatamapping_relation_patterns_association
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