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pythonsqlsqlalchemymany-to-many

How to query for empty records in many to many relation

class BlogPost(SchemaBase):
  id = Column(Integer, primary_key=True)
  name    = Column(String,  unique=True)
  authors = relationship('Authors', secondary='authors_to_blog_post')
  __tablename__ = 'blogpost'

class Authors(SchemaBase):
  id = Column(Integer, primary_key=True)
  name    = Column(String,  unique=True)
  __tablename__ = 'author'

authors_to_blog_post = Table('authors_to_blog_post', Base.metadata,
    Column('author_id', Integer, ForeignKey('author.id')),
    Column('blogpost_id', Integer, ForeignKey('blogpost.id'))
    )

Now how to query for all blogposts without any author? session.query(BlogPost).filter(BlogPost.authors == []) doesnt work

Solution

  • Found answer from here: https://groups.google.com/d/msg/sqlalchemy/Ow0bb6HvczU/VVQbtd7MnZkJ

    So the solution is

    session.query(BlogPost).filter(~BlogPost.authors.any())