CODEWITHSUNDEEP
pythonflasksqlalchemyflask-sqlalchemy
Eddie An
Eddie An

Reputation: 1

How can you map multiple tables to one model?

If I have two tables with same columns, ex. a table called Toyota and a table called Honda, how can I map these two tables with one model (maybe called Car) in flask?

Upvotes: 0

Views: 972

Answers (2)

davidism
davidism

Reputation: 127180

While you can map multiple tables to a single class, what you are asking for is probably better solved with inheritance. There are two main types of inheritance: joined or single table. Since your example says that the type is the only thing different, all other columns being the same, single table seems more appropriate.

class Car(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    type = db.Column(db.String, nullable=False)
    wheels = db.Column(db.Integer, nullable=False, default=4)

    __mapper_args__ = {
        'polymorphic_on': type,
    }


class TeslaModelS2014(Car):
    __mapper_args__ = {
        'polymorphic_identity': 'Tesla Model S 2014',
    }

This is a really contrived example; inheritance isn't really appropriate at all here. All cars can be represented without making subclasses. If you have subclasses, you have to make one for each make/model/year in existence, which is ridiculous.

Upvotes: 3

Matt Healy
Matt Healy

Reputation: 18531

If you have two tables with the same columns, your database schema could probably be done better. I think you should really have a table called CarMake, with entries for Toyota, Honda etc, and another table called Car which has a foreign key to CarMake (e.g. via a field called car_make or similar).

That way, you could represent this in Flask with two models - one for Car and one for CarMake.

Upvotes: 1

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