flask-sqlalchemy 中的多重关系

Question

hi i am trying to create a flask app using flask-sqlalchemy as the database(from tech with tim tutorials). There are two classes notes and users each user can have a single note and the code for it is given below this works perfectly fine but when i tried to create a contacts class such that each user can have contacts log(a part of the app that i am building).It is returning a NO FOREIGN KEYS ERROR.How to go aobut fixing this problem??

code

    from . import db
    from flask_login import UserMixin
    from sqlalchemy.sql import func

    #child class

     class Contact(db.Model):
         id = db.Column(db.Integer, primary_key=True)
         city=db.Column(db.String(10000))
         addr=db.Column(db.String(10000))
         contacts_id=db.Column(db.Integer,db.ForeignKey('contacts.id'))

     class Note(db.Model):
         id = db.Column(db.Integer, primary_key=True)
         data = db.Column(db.String(10000))
         date = db.Column(db.DateTime(timezone=True), default=func.now())
         user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
     class User(db.Model, UserMixin):
         id = db.Column(db.Integer, primary_key=True)
         email = db.Column(db.String(150), unique=True)
         password = db.Column(db.String(150))
         first_name = db.Column(db.String(150))
         notes = db.relationship('Note')
         contact=db.relationship('Contact')

Answer 1

Have a look at Miguel Ginberg's Flask mega tutorial in the 'Database relationships' section for one-to-many relationships .

Look at the Followers, Contacts and Friends section for many-to-many relationships.