Many-to-many relationships in Flask - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the association table for a many-to-many relationship in Flask-SQLAlchemy.

Flask

association_table = db.Table('association',
    db.Column('left_id', db.Integer, db.ForeignKey('left.id')),
    db.Column('right_id', db.Integer, [1]('right.id'))
)

Drag options to blanks, or click blank then click option'

AForeignKey

Brelationship

CColumn

DInteger

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'relationship' instead of 'ForeignKey' in the association table columns.

Forgetting to use 'ForeignKey' causes errors linking tables.

The ForeignKey is used to link columns in the association table to the primary keys of the related tables.

2fill in blank

medium

Complete the code to define a many-to-many relationship in a Flask model using SQLAlchemy.

Flask

class Parent(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    children = db.relationship('[1]', secondary=association_table, back_populates='parents')

Drag options to blanks, or click blank then click option'

AParents

Bchild

Cchildren

DChild

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase or plural names instead of the exact class name.

Confusing the attribute name with the class name.

The relationship function takes the name of the related model class as a string, which is case-sensitive and usually singular.

3fill in blank

hard

Fix the error in the relationship definition to correctly link both sides of a many-to-many relationship.

Flask

class Child(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    parents = db.relationship('Parent', secondary=association_table, [1]='children')

Drag options to blanks, or click blank then click option'

Abackref

Bforeign_keys

Cback_populates

Dlazy

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'backref' instead of 'back_populates' when both sides are declared.

Omitting the linking keyword causes relationship errors.

back_populates is used to explicitly link two relationship properties on different models for a many-to-many relationship.

4fill in blank

hard

Fill both blanks to create a many-to-many relationship with a custom association table and back_populates.

Flask

class Author(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    books = db.relationship('[1]', secondary=[2], back_populates='authors')

Drag options to blanks, or click blank then click option'

ABook

Bauthor_book

CAuthorBook

Dbook_author

Attempts:

3 left

💡 Hint

Common Mistakes

Using the class name of the association table instead of the table variable.

Mixing up the order of blanks.

The first blank is the related model class name 'Book'. The second blank is the name of the association table variable, here 'author_book'.

5fill in blank

hard

Fill all three blanks to define a many-to-many relationship with a custom association table and back_populates on both models.

Flask

class Book(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    authors = db.relationship('[1]', secondary=[2], back_populates='[3]')

Drag options to blanks, or click blank then click option'

AAuthor

Bauthor_book

Cbooks

Dauthors

Attempts:

3 left

💡 Hint

Common Mistakes

Using plural for the related model name.

Confusing the back_populates attribute name.

The related model is 'Author', the association table is 'author_book', and the back_populates attribute on Author is 'books'.