Here is the full code:
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import *
from sqlalchemy.orm import relationship, sessionmaker
Base = declarative_base()
product_tags = Table(
'product_tags', Base.metadata,
Column('product_id', Integer, ForeignKey('products.id')),
Column('tag_id', Integer, ForeignKey('tags.id'))
)
class Tag(Base):
__tablename__ = 'tags'
id = Column(Integer, primary_key=True)
name = Column(Unicode(20))
products = relationship("Product", secondary=product_tags)
class Product(Base):
__tablename__ = 'products'
id = Column(Integer, primary_key=True)
name = Column(Unicode(20))
tags = relationship("Tag", secondary=product_tags)
engine = create_engine('postgresql://user:password@localhost/example')
Session = sessionmaker(bind=engine)
Base.metadata.drop_all(engine)
Base.metadata.create_all(engine)
p1 = Product(name = 'Milk')
p2 = Product(name = 'Water')
tag1 = Tag(name='Liquid')
p1.tags.append(tag1)
p2.tags.append(tag1)
s = Session()
s.add_all([p1, p2, tag1])
s.commit()
s.close()
s = Session()
s.delete(s.query(Tag).first())
s.commit()
s.close()
After it runs, the product_tags table is completely empty.
From: sqlalchemy@googlegroups.com [mailto:sqlalchemy@googlegroups.com] On
Behalf Of Jonathan Vanasco
Sent: Friday, December 06, 2013 6:07 PM
To: sqlalchemy@googlegroups.com
Subject: [sqlalchemy] Re: Many2many, referential integrity and introspection
can you share your existing schema for these relations ?
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