Hi,
I am currently trying to use an SQL expression as a mapped attribute. I have
a table called species_table and a species_names_tables, there is a one to
many relationship between them on species_table.c.taxa_id and
species_names_table.c.taxa. So one species can have multiple names. I am
currently trying to make it so that a Species object has an attribute called
"names" which is a list of the names held in the species_table (there are
other attributes in this table, but I don't want any of them). So this is
what I ve tried to do:
mapper(Species, select([species_table],
species_table.c.rank=='species').alias('speciesfooalias'),
properties={'names':column_property(select([species_names_table.c.name],
species_table.c.taxa_id==species_names_table.c.taxa).label("names"))})
#metadata.create_all(engine)
session = Session()
s =session.query(Species).filter(Species.taxa_id==7).one()
this is the problem, because now it says that
raise exceptions.InvalidRequestError('No rows returned for one()')
sqlalchemy.exceptions.InvalidRequestError: No rows returned for one()
however if I just do it using a simple mapper with no column_property:
mapper(Species, select([species_table],
species_table.c.rank=='species').alias('speciesfooalias'))
I get the correct output. I am using SQLAlchemy 0.4.8
I am pretty confused by this. Any help is very much appreciated.
Many thanks in advance,
Nathan
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