[sqlalchemy] 테이블간 relationship 설정

 

테이블간 one to many등과 같은 관계가 있을때,

sqlslachemy의 relationship을 통해서 해당 관계를 지정할 수 있다. 

테이블을 생성할 때 추가해주면 된다. 

 

공식문서:

https://docs.sqlalchemy.org/en/14/orm/basic_relationships.html

 

Relationship 설정 1 - #backref 사용하기

relationship('Class명', backref ='해당테이블 명')

class User(Base):

    __tablename__ = 'user'

    id = Column(Integer, primary_key=True)
    screen_name = Column(String)
    tweets = relationship('Tweet', backref='user')

    def __repr__(self):
        return f"User({self.id})"


class Tweet(Base):


    __tablename__ = 'tweet'

    id = Column(Integer, primary_key=True)
    full_text = Column(String)
    user_id = Column(Integer, ForeignKey('user.id'))

    def __repr__(self):
        return f"Tweet({self.id})"

 

 

 

Relationship 설정 1 - #back_populates사용하기 

pair 짝이 맞아야하고, back_populates에 적은 name명이 같아야 한다. 

 

 

tweet_ = db.relationship('Tweet', back_populates = 'user_', cascade='all, delete')

user_ = db.relationship('User', back_populates = 'tweet_')

 

 

class Address(Base):
    __tablename__ = "Address"

    address_id = Column(Integer, primary_key=True, nullable=False)
    city = Column(String(48))
    street = Column(String(128))
    customer_id = Column(Integer, ForeignKey('Customer.customer_id'))

    invoice_Item = relationship('Invoice_Item', back_populates='address', cascade='all, delete') #primary - 0ne:Many 에서 one쪽


class Invoice_Item(Base):
    __tablename__ = 'Invoice_Item'
    ii_id = Column(Integer, primary_key=True, nullable=False)
    invoice_date = Column(DateTime, nullable=False)
    address_id = Column(Integer, ForeignKey('Address.address_id'))
    item_id = Column(Integer, ForeignKey('Item.item_id'))

    address = relationship('Address', back_populates='invoice_Item')

 

foreign Key에서는 Table명,

relationship에서는 Class명으로 설정한다