Hi there,
I have a bunch of mysql tables.
Up to now I did not define their structure in python but used
Base.metadata.reflect(engine)
No I started to define their structure in Python and stumbled over the fact,
that I do not understand
how ForeignKeyConstraint should be used correctly.
The following tables
tblPerson, tblFlag
are linked using the association table tblPerson_has_Flag.
this works fine if I explicitly define columns to be part of foreign keys as
shown in tblPerson_has_Flag below.
what I wanted to do, but failed was:
in tblPerson_has_Flag insted of marking the columns to be part of a fk to have
the following construct
__table_args__ = (
sa.ForeignKeyConstraint(
['tblPerson_id'], [u'tblPerson.id'],
['tblFlag_id'], [u'tblFlag.id'],
),
sa.PrimaryKeyConstraint(u'tblPerson_id', u'tblFlag_id'), {}
)
However, if I do so, I get an sqlalchemy.exc.NoForeignKeysError: Could not
determine join condition between parent/child
error
how should I use ForeignKeyConstraint correctly?
thanks
robert
## ----------------------------------------------------------------------------
## flags
## ----------------------------------------------------------------------------
class tblPerson(Base):
__tablename__ = 'tblPerson'
id = sa.Column( mysql.INTEGER(display_width=11), nullable=False)
lastname = sa.Column( mysql.VARCHAR(length=124), nullable=False)
firstname = sa.Column( mysql.VARCHAR(length=45), server_default='',
nullable=True)
...
__table_args__ = (
sa.PrimaryKeyConstraint(u'id'), {}
)
class tblPerson_has_Flag(Base):
__tablename__ = 'tblPerson_has_Flag'
tblPerson_id = sa.Column( mysql.INTEGER(display_width=11),
sa.ForeignKey('tblPerson.id'),
autoincrement=False, nullable=False)
tblFlag_id = sa.Column( mysql.INTEGER(display_width=11),
sa.ForeignKey('tblFlag.id'),
autoincrement=False, nullable=False)
__table_args__ = (
#sa.ForeignKeyConstraint(
#['tblPerson_id'], [u'tblPerson.id'],
#['tblFlag_id'], [u'tblFlag.id'],
#),
sa.PrimaryKeyConstraint(u'tblPerson_id', u'tblFlag_id'), {}
)
class tblFlag(Base):
__tablename__ = 'tblFlag'
id = sa.Column( mysql.INTEGER(display_width=11), nullable=False)
name = sa.Column( mysql.VARCHAR(length=124), nullable=False)
flag = sa.Column( mysql.TINYINT(display_width=1), server_default='0',
autoincrement=False, nullable=False)
description = sa.Column( mysql.VARCHAR(length=245), server_default='',
nullable=True)
__table_args__ = (
sa.PrimaryKeyConstraint(u'id'), {}
)
flagged_persons = relationship(
'tblPerson',
secondary=tblPerson_has_Flag.__table__,
backref="flags",
#collection_class=attribute_mapped_collection('id')
)
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