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 <sector...@gmail.com> 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 > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sqlalchemy+unsubscr...@googlegroups.com. > To post to this group, send email to sqlalchemy@googlegroups.com. > Visit this group at https://groups.google.com/group/sqlalchemy. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.