SQLAlchemy：检查两列之一的约束是否不为null？ [英] SQLAlchemy: Any constraint to check one of the two columns is not null?

问题描述

这可能完全是愚蠢的事情，但是我的模型中有这样一个要求，其中至少类别或 parent_category 不为空

This may be totally stupid thing to ask but I have such a requirement in my model where atleast either category or parent_category is not null

我的模型如下

class BudgetCategories(db.Model):
    __tablename__ = 'budget_categories'
    uuid = Column('uuid', GUID(), default=uuid.uuid4, primary_key=True,
                  unique=True)
    budget_id = Column(GUID(), ForeignKey('budgets.uuid'), nullable=False)
    budget = relationship('Budget', backref='budgetCategories')
    category = Column('category', sa.types.String, nullable=True)
    parent_category = Column('parent_category', sa.types.String, nullable=True)
    amount = Column('amount', Numeric(10, 2), nullable=False)
    recurring = Column('recurring', sa.types.Boolean,
                       nullable=False)
    created_on = Column('created_on', sa.types.DateTime(timezone=True),
                        nullable=False)

我该如何指定。我什至不知道该怎么尝试

How can I specify that. I don't even know what to try

任何指针都得到赞赏

我正在使用 PostgreSQL 作为后端数据库

I am using PostgreSQL as the backend database

推荐答案

对于<$ c $，我不确定100％ c> PostgreSQL 语法，但是在添加到 BudgetCategories 模型之后，应该使用 CheckConstraint ：

I am not 100% sure about the PostgreSQL syntax, but following addition to your BudgetCategories model should do the trick using CheckConstraint:

class BudgetCategories(Base):
    __tablename__ = 'budget_categories'
    # ...

    # @note: new
    __table_args__ = (
            CheckConstraint('NOT(category IS NULL AND parent_category IS NULL)'),
            )

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