I don't understand that error - you're asking it to join along predefined
relationships, so it shouldn't need to search for foreign keys at query
time. "Category.products" is a relationship set up as the backref of
Product.categories.
Here's a working example. I had to add the definition of the many-to-many
table.
import sqlalchemy as sa
from sqlalchemy import Column, Integer, UnicodeText, ForeignKey
import sqlalchemy.orm as saorm
from sqlalchemy.orm import relationship
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class Brand(Base):
__tablename__ = 'brand'
id = Column(Integer, primary_key=True)
name = Column(UnicodeText, nullable=False)
slug = Column(UnicodeText, nullable=False, unique=True)
class Category(Base):
__tablename__ = 'category'
id = Column(Integer, primary_key=True)
name = Column(UnicodeText, nullable=False)
product_category = sa.Table(
'product_category',
Base.metadata,
Column('product_id', ForeignKey('product.id')),
Column('category_id', ForeignKey('category.id')),
)
class Product(Base):
__tablename__ = 'product'
id = Column(Integer, primary_key=True)
brand_id = Column(Integer, ForeignKey('brand.id'), nullable=False)
name = Column(UnicodeText, nullable=False)
brand = relationship('Brand', backref='products')
categories = relationship('Category', backref='products',
secondary=product_category) # many-to-many relationship
if __name__ == '__main__':
engine = sa.create_engine('sqlite://')
Base.metadata.create_all(bind=engine)
Session = saorm.sessionmaker(bind=engine)
session = Session()
brand_slug = 'some_slug'
q = session.query(Category).join('products',
'brand').filter(Brand.slug==brand_slug)
print q
print q.all()
On Wed, Mar 2, 2016 at 6:09 AM, sector119 <[email protected]> wrote:
> With that query I get:
> InvalidRequestError: Could not find a FROM clause to join from. Tried
> joining to <class 'supplements.models.Product'>, but got: Can't find any
> foreign key relationships between 'category' and 'product'.
>
> Product and category model has many to many relationship
>
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