Sqlalchemy : association table for many-to-many relationship between groups and members. How can I delete a relationship?

Question

I have those tables setup : http://pastie.org/627764

...    
    # This is the association table for the many-to-many relationship between
    # groups and members - this is, the memberships.
    user_group_table = Table('user_group', metadata,
        Column('user_name', Integer, ForeignKey('user.user_name',
            onupdate="CASCADE", ondelete="CASCADE")),
        Column('group_name', Integer, ForeignKey('group.group_name',
            onupdate="CASCADE", ondelete="CASCADE"))
    )

    class Group(DeclarativeBase):

        __tablename__ = 'group'

        group_name = Column(Unicode(16), primary_key=True)

        users = relation('User', secondary=user_group_table, backref='groups')
...

I'm trying to delete the relation between one user and one of his group but I can't really come up with a query that does it. Any way to do this using Sqlalchemy?

Thanks for your time.

Answer 1

You mean you want to remove a User from a Group?

# fetch the mapped classes
group = Session.query(Group).some_filters().one()
user = Session.query(User).some_filters().one()

# group.users is a list of all users in this group
# remove one and it will be removed from the DB
group.users.remove( user )
Session.commit()