在 Flask SQL Alchemy 中编写复合键 [重复]

Question

我的桌子如下所示：

class Dummies(db.Model):

    __tablename__ = 'dummies'

    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    name = db.Column(db.String(100), index=True, nullable=True)
    value = db.Column(db.String(100), index=True, nullable=True)
    sum_id = db.Column(db.Integer, db.ForeignKey('pattern.id',
                                                      onupdate='CASCADE',
                                                      ondelete='CASCADE'),
                                                      index=True, nullable=False)

我对烧瓶很陌生，并试图绕过这种关系的语法，我想代表。我想使用名称、值和 sum_id 来唯一地表示一行。有人可以帮我写这个关系吗？

Answer 1

如果你想对多列强制执行唯一约束，你可以像这样显式设置它：

    __tablename__ = 'dummies'

    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(100), nullable=True)
    value = db.Column(db.String(100), nullable=True)
    sum_id = db.Column(db.Integer, db.ForeignKey('pattern.id'), nullable=False)                                                                                                      
    UniqueConstraint('name', 'value', 'sum_id'
                                 name='myMultipleColumnUniqueConstraint')

这样您可以强制执行多列唯一性约束。也只是想指出 onupdate => refers to a default value for the column. 据我所知，sqlAlchemy 中没有 ondelete。但你可以使用：

  cascade = "all, delete-orphan" ``` 
on Parent Table relationship to achieve the same effect as ondelete="cascade" as in django. 

类 ParentDummies(db.Model): dummies= relationship("Dummy", cascade="all, delete-orphan")

Also, if you are trying make those columns as composite primary key, you can do so like this: 
```  class Dummies(db.Model):

    __tablename__ = 'dummies'

    id = db.Column(db.Integer)
    name = db.Column(db.String(100), nullable=True)
    value = db.Column(db.String(100), nullable=True)
    sum_id = db.Column(db.Integer, db.ForeignKey('pattern.id', nullable=False),
    PrimaryKeyConstrain('name', 'value', 'sum_id', name="myCompositePk")                              

或

class Dummies(db.Model):

    __tablename__ = 'dummies'

    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    name = db.Column(db.String(100), nullable=True, primary_key=True)
    value = db.Column(db.String(100), nullable=True, primary_key=True)
    sum_id = db.Column(db.Integer, db.ForeignKey('pattern.id'), nullable=False, primary_key=True)