代码：
from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://root:xxxxxx@localhost/flasky'
app.config['SQLALCHEMY_COMMIT_ON_TEARDOWN'] = True
db = SQLAlchemy(app)
class Role(db.Model):
__tablename__ = 'roles'
id = db.Column(db.Integer,primary_key = True)
name = db.Column(db.String(64), unique = True)
users = db.relationship('User', backref = 'role') #这行建立一对多的反向关系时出错
def __repr__(self):
return '<Role %r>' % self.name
class User(db.Model):
__tablename__ = 'users'
id = db.Column(db.Integer, primary_key = True)
username = db.Column(db.String(64), unique = True)
role_id = db.column(db.Integer, db.ForeignKey('roles.id'))
def __repr__(self):
return '<User %r>' % self.username
if __name__ == '__main__':
app.run()
出错提示：
sqlalchemy.exc.NoForeignKeysError: Could not determine join condition between parent/child tables on relationship Role.users - there are no foreign keys linking these tables. Ensure that referencing columns are associated with a ForeignKey or ForeignKeyConstraint, or specify a 'primaryjoin' expression.
提示没有建立外键，但是我明明在User里面建立了一个叫role_id的外键，求解
__python版本是3.5.0 数据库是mysql
