Python sqlalchemy hybrid_性质与表达式
我听不懂这些表达。如何让下面的代码工作Python sqlalchemy hybrid_性质与表达式,python,sqlalchemy,Python,Sqlalchemy,我听不懂这些表达。如何让下面的代码工作 class OperationType(Enum): MINUS = 1 MINUS_CORR = 2 PLUS = 3 PLUS_CORR = 4 按类型分组操作 BALANCE_PLUS_OPERATIONS = [ OperationType.PLUS.value, OperationType.PLUS_CORR.value ] BALANCE_MINUS_OPERATIONS = [ Op
class OperationType(Enum):
MINUS = 1
MINUS_CORR = 2
PLUS = 3
PLUS_CORR = 4
按类型分组操作
BALANCE_PLUS_OPERATIONS = [
OperationType.PLUS.value,
OperationType.PLUS_CORR.value
]
BALANCE_MINUS_OPERATIONS = [
OperationType.MINUS.value,
OperationType.MINUS_CORR.value
]
运营模式
class Operation(Model):
__tablename__ = 'operation'
id = db.Column(db.BigInteger, primary_key=True)
created_at = Column(db.DateTime, nullable=False, default=dt.datetime.utcnow)
operation_type = db.Column(db.SmallInteger, nullable=False)
amount = Column(db.Integer, nullable=False)
user_id = db.Column(db.ForeignKey('users.id'), nullable=False)
user = relationship('User', backref='operation', uselist=False)
用户模型
class User(UserMixin, Model):
__tablename__ = 'users'
id = Column(db.Integer, primary_key=True)
operations = relationship("Operation", backref="users")
@hybrid_property
def balance(self):
plus = sum(op.amount for op in self.operations if op.operation_type in BALANCE_PLUS_OPERATIONS)
minus = sum(op.amount for op in self.operations if op.operation_type in BALANCE_MINUS_OPERATIONS)
return plus - minus
@balance.expression
def balance(cls):
p = select([func.sum(Operation.amount).label('BALANCE_PLUS_OPERATIONS')]) \
.where(Operation.operation_type.in_(BALANCE_PLUS_OPERATIONS)) \
.where(User.id == cls.id) \
.as_scalar()
m = select([func.sum(Operation.amount).label('BALANCE_MINUS_OPERATIONS')]) \
.where(Operation.operation_type.in_(BALANCE_MINUS_OPERATIONS)) \
.where(User.id == cls.id) \
.as_scalar()
return select([p - m]).label('BALANCE')
表达式错误,将产生错误的结果:
users = User.query.filter_by(balance=51).all()
for u in users:
print(u, u.balance)
打印:
<User(foo@bar.com)> 51
<User(bar@foor.com)> 0
51
0
但我只希望有一张唱片:
<User(foo@bar.com)> 51
51
谢谢我将根据上下文假设这些方法属于
用户
类。在那种情况下
.where(User.id == cls.id) \
有效地
.where(User.id == User.id) \
或者只是where(True)
,这样每个用户都会参与到每个操作中,而这些操作可能与
.where(Operation.user_id == cls.id) \
虽然由于缺乏实例而无法说明。如果确实发生了不正确的联接,它将解释查询返回另一个用户的原因:它与属于正确用户的操作联接
您可能还需要添加
.correlate(cls) \
在之前作为\u scalar()
。我认为最外层的select也是多余的。你应该能够
return (p - m).label('BALANCE')
请编辑您的问题,以解释(1)您预期会发生什么,(2)您将得到什么错误(或结果如何不同)和(3)将问题缩小到问题中的代码。阅读会有帮助的。非常感谢!我需要什么。一个站点没有提供发布所有代码的权限。基本用户和操作中有两个表。并且用户有很多操作。