On Mon, Sep 30, 2019, at 12:25 AM, Mateja Putic wrote:
> I would like to create an association between a Dataset object and all
> Category objects through an intermediate Annotation table.
> A Dataset contains a collection of Annotations. Each Annotation has a single
> Category. I want Dataset.categories to contain the unique set of Categories
> made up of all the Categories of all the Annotations in that Dataset. I have
> tried doing this with a double association table (`dataset_categories`), but
> it is not working. What is the right way to do this? Here is my code so far:
hello -
your code looks fine although I have not carefully parsed your rather complex
statement of intent. Can you provide specifics for "not working" please and do
you have a specific database schema designed in order to achieve what you are
looking for? if you have a general database schema design issue you will get
more help on stack overflow.
> `Base = declarative_base()
dataset_categories = Table('dataset_categories', Base.metadata,
Column('dataset_id', Integer, ForeignKey('datasets.id')),
Column('annotation_id', Integer, ForeignKey('annotations.id')),
Column('category_id', Integer, ForeignKey('categories.id')))
> class Dataset(Base):
__tablename__ = 'datasets'
id = Column(Integer, primary_key=True)
annotations = relationship("Annotation")
categories = relationship("Category", secondary=dataset_categories)
> class Annotation(Base):
__tablename__ = 'annotations'
id = Column(Integer, primary_key=True)
category_id = Column(Integer, ForeignKey('categories.id'), nullable=False)
category = relationship("Category")
dataset_id = Column(Integer, ForeignKey('datasets.id'))
> class Category(Base):
__tablename__ = 'categories'
id = Column(Integer, primary_key=True)
name = Column(String, nullable=False, unique=True)
dataset = relationship("Dataset", secondary=dataset_categories)
dataset_id = Column(Integer, ForeignKey('datasets.id'),
back_populates='categories')`
>
> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
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> To post example code, please provide an MCVE: Minimal, Complete, and
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SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
To post example code, please provide an MCVE: Minimal, Complete, and Verifiable
Example. See http://stackoverflow.com/help/mcve for a full description.
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