["python","flask","sqlalchemy","flask-sqlalchemy"]
Flask sqlalchemy many-to-many insert data

I am trying to make a many to many relation here in Flask-SQLAlchemy, but it seems that I don't know how to fill the "many to many identifier database". Could you please help me understand what I am doing wrong and how it is supposed to look? class User(db.Model): __tablename__ = 'users' user_id = db.Column(db.Integer, primary_key=True) user_fistName = db.Column(db.String(64)) user_lastName = db.Column(db.String(64)) user_email = db.Column(db.String(128), unique=True) class Class(db.Model): __tablename__ = 'classes' class_id = db.Column(db.Integer, primary_key=True) class_name = db.Column(db.String(128), unique=True) and then my identifier database: student_identifier = db.Table('student_identifier', db.Column('class_id', db.Integer, db.ForeignKey('classes.class_id')), db.Column('user_id', db.Integer, db.ForeignKey('users.user_id')) ) so far it looks like this when I try to insert the data into the database. # User user1 = User( user_fistName='John', user_lastName='Doe', user_email='john@doe.es') user2 = User( user_fistName='Jack', user_lastName='Doe', user_email='jack@doe.es') user3 = User( user_fistName='Jane', user_lastName='Doe', user_email='jane@doe.es') db.session.add_all([user1, user2, user3]) db.session.commit() # Class cl1 = Class(class_name='0A') cl2 = Class(class_name='0B') cl3 = Class(class_name='0C') cl4 = Class(class_name='Math') cl5 = Class(class_name='Spanish') db.session.add_all([cl1, cl2, cl3, cl4, cl5]) db.session.commit() Now my problem is, how do I add to the many to many database, since I really can't create a 'student_identifier' object? If I could it could perhaps have looked like this: # Student Identifier sti1 = StiClass(class_id=cl1.class_id, class_name=user1.user_id) sti2 = StiClass(class_id=cl3.class_id, class_name=user1.user_id) sti3 = StiClass(class_id=cl4.class_id, class_name=user1.user_id) sti4 = StiClass(class_id=cl2.class_id, class_name=user2.user_id) db.session.add_all([sti1, sti2, sti3, sti4]) db.session.commit() How I am supposed to insert into a many to many table with ORM?
You don't need to add anything directly to your association table, SQLAlchemy will do that. This is more or less from SQLAlchemy documentations: association_table = db.Table('association', db.Model.metadata, db.Column('left_id', db.Integer, db.ForeignKey('left.id')), db.Column('right_id', db.Integer, db.ForeignKey('right.id')) ) class Parent(db.Model): __tablename__ = 'left' id = db.Column(db.Integer, primary_key=True) children = db.relationship("Child", secondary=association_table) class Child(db.Model): __tablename__ = 'right' id = db.Column(db.Integer, primary_key=True) p = Parent() c = Child() p.children.append(c) db.session.add(p) db.session.commit() Therefore your sample would be like this: student_identifier = db.Table('student_identifier', db.Column('class_id', db.Integer, db.ForeignKey('classes.class_id')), db.Column('user_id', db.Integer, db.ForeignKey('students.user_id')) ) class Student(db.Model): __tablename__ = 'students' user_id = db.Column(db.Integer, primary_key=True) user_fistName = db.Column(db.String(64)) user_lastName = db.Column(db.String(64)) user_email = db.Column(db.String(128), unique=True) class Class(db.Model): __tablename__ = 'classes' class_id = db.Column(db.Integer, primary_key=True) class_name = db.Column(db.String(128), unique=True) students = db.relationship("Student", secondary=student_identifier) s = Student() c = Class() c.students.append(s) db.session.add(c) db.session.commit()