On Jul 24, 2012, at 11:25 AM, Enrico Morelli wrote:
> Dear all,
>
> I've the following tables:
>
> site_table = Table('site', metadata,
> Column('id', types.Integer, primary_key=True),
> Column('name', types.Unicode(15), nullable=False))
>
> chain_table = Table('chain', metadata,
> Column('id', types.Integer, primary_key=True),
> Column('letter', types.Unicode(1), nullable=False),
> Column('ec_number', types.Unicode(50), nullable=True))
>
> sites_chains_table = Table('sites_chains', metadata,
> Column('site_id', types.Integer,
> ForeignKey('site.id'),primary_key=True),
> Column('chain_id', types.Integer,ForeignKey('chain.id'),
> primary_key=True))
>
> and the following mappers:
>
> mapper(Site, site_table,
> properties={'chain': relationship(Chain, backref='site',
> secondary=sites_chains_table), })
>
> mapper(Chain, chain_table)
>
> Which query I've to write to count all site where
> chain.ec_number==something using its relation.
query(Site).join(Site.chain).filter(Chain.ec_number==something).count()
see this recent stackoverflow answer:
http://stackoverflow.com/a/11568381/34549
>
> I tried to do something like:
> count =
> Session.query(func.count(Site.id)).filter(Chain.ec_number==ec_number).filter(Site.chain.any(id=Chain.id)).all()
>
> but the result isn't real.
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