Flask 学习-84.Flask-SQLAlchemy 一对多关系级联删除

前言

一对多关系，当删除主表数据的时候，关联表数据一起删除掉

一对多

模型设计

class Person(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(50))
    addresses = db.relationship('Address', backref='person', cascade="all,delete")


class Address(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(50))
    person_id = db.Column(db.Integer, db.ForeignKey('person.id'))

主要是在 relationship 加一个cascade="all,delete" 属性

其它关联删除方式

    ###  只删除父级，子不影响
    # 1. addresses = db.relationship('Address', backref='person',  passive_deletes=True)

    ###  子级跟随删除
    # 2. addresses = db.relationship('Address', backref='person', cascade="all, delete-orphan")
    # 3. addresses = db.relationship('Address', backref='person', cascade="all, delete")

    ##  父级删除，子级不删除，外键更新为 null
    # 4. addresses = relationship("Address", backref = backref("child"))

新增与删除

新增数据

        person = Person(name='yoyo')
        person.addresses = [
            Address(email='123@qq.com')
        ]
        db.session.add(person)
        db.session.commit()  # 提交

删除Person 表数据，关联表一并删除

        p = Person.query.filter_by(name='yoyo').first()
        db.session.delete(p)
        db.session.commit()