本文介绍了在SQLAlchemy中遇到的两个模型没有外键关联但仍尝试进行JOIN操作时的错误。当尝试从`Users`模型查询并JOIN到`TimeOff`模型时，出现InvalidRequestError，提示找不到JOIN的FROM子句。解决方案是在JOIN查询时明确指定JOIN条件，例如：`result = db.session.query(Users).join(TimeOff, Users.userName == TimeOff.userName)`。这允许SQLAlchemy理解如何在没有外键的情况下连接两个表格。
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
解决方案
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)
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