Flask SqlAlchemy join two models without foreign key MYSQL

问题

I am joining two models without a foreign key:

Models:

class Users(db.Model):
    __tablename__ = "Users"
    userName = db.Column(db.String, primary_key=True)
    lastLogin = db.Column(db.DateTime)

class TimeOff
    __tablename__ = "timeOff"
    timeOffID = db.Column(db.Integer, primary_key=True)
    userName = db.Column("userName", db.String,   db.ForeignKey('appUsers.userName')),
    dayWork = db.Column(db.DateTime)

View:

result = db.session.query(models.Users).join(models.TimeOff)

sqlalchemy.exc.InvalidRequestError: Could not find a FROM clause to join from. Tried joining to but got: Can't find any foreign key relationships between 'TimeOff' and 'Users'.

I dont have a foreign key defined in table

回答1:

You need to tell SQLAlchemy how to join the tables. Try something like this:

result = db.session.query(Users).join(TimeOff,Users.userName==TimeOff.userName)

回答2:

To improve upon @Matt Healy's answer, if you also want to be able to access attributes on the joined object you can do something like:

user, timeOff = db.session.query(Users, TimeOff).join(
    TimeOff, Users.userName == TimeOff.userName
).first()

Then timeOff.dayWork etc. will give the information you need.

来源：https://stackoverflow.com/questions/30791708/flask-sqlalchemy-join-two-models-without-foreign-key-mysql