问题
I'm having a lot of trouble getting my head around foreign keys and relationships in SQLAlchemy. I have two tables in my database. The first one is Request
and the second one is Agent
. Each Request
contains one Agent
and each Agent
has one Request
.
class Request(db.Model):
__tablename__ = 'request'
reference = db.Column(db.String(10), primary_key=True)
applicationdate = db.Column(db.DateTime)
agent = db.ForeignKey('request.agent'),
class Agent(db.Model):
__tablename__ = 'agent'
id = db.relationship('Agent', backref='request', \
lazy='select')
name = db.Column(db.String(80))
company = db.Column(db.String(80))
address = db.Column(db.String(180))
When I am running db.create_all()
I get the following error
Could not initialize target column for ForeignKey 'request.agent' on table 'applicant': table 'request' has no column named 'agent'
回答1:
Have a look at the SqlAlchemy documentation on OneToOne relationships. First you need to supply a primary key for each Model. Then you need to define one foreign key which refers to the Primary Key of the other model. Now you can define a relationship with a backref that allows direct access to the related model.
class Request(db.Model):
__tablename__ = 'request'
id = db.Column(db.Integer, primary_key=True)
applicationdate = db.Column(db.DateTime)
class Agent(db.Model):
__tablename__ = 'agent'
id = db.Column(db.Integer, primary_key=True)
request_id = Column(Integer, ForeignKey('request.id'))
request = relationship("Request", backref=backref("request", uselist=False))
name = db.Column(db.String(80))
company = db.Column(db.String(80))
address = db.Column(db.String(180))
Now you can access your models like this:
request = Request.query.first()
print(request.agent.name)
agent = Agent.query.first()
print(agent.request.applicationdate)
来源:https://stackoverflow.com/questions/41569206/flask-sqlalchemy-foreign-key-relationships