관계 제거하기
관계 제거하기 (Remove Relationships)
이제 Spider-Boy가 Rusty-Man에게 이렇게 말한다고 해볼게요:
나는 몸 상태가 좋지 않아요, Mr. Sharp
그리고 어떤 이유로든 몇 년 동안 Preventers를 떠나야 한다고요. 😭
출처: 공식문서
관계를 None으로 설정해서 제거할 수 있어요. team_id와 마찬가지로, 새로운 관계 속성 .team에서도 동일하게 동작해요:
# Code above omitted 👆
def update_heroes():
with Session(engine) as session:
statement = select(Hero).where(Hero.name == "Spider-Boy")
result = session.exec(statement)
hero_spider_boy = result.one()
hero_spider_boy.team = None
session.add(hero_spider_boy)
session.commit()
session.refresh(hero_spider_boy)
print("Spider-Boy without team:", hero_spider_boy)
# Code below omitted 👇
👀 전체 파일 미리보기 (Full file preview)
from sqlmodel import Field, Relationship, Session, SQLModel, create_engine, select
class Team(SQLModel, table=True):
id: int | None = Field(default=None, primary_key=True)
name: str = Field(index=True)
headquarters: str
heroes: list["Hero"] = Relationship(back_populates="team")
class Hero(SQLModel, table=True):
id: int | None = Field(default=None, primary_key=True)
name: str = Field(index=True)
secret_name: str
age: int | None = Field(default=None, index=True)
team_id: int | None = Field(default=None, foreign_key="team.id")
team: Team | None = Relationship(back_populates="heroes")
sqlite_file_name = "database.db"
sqlite_url = f"sqlite:///{sqlite_file_name}"
engine = create_engine(sqlite_url, echo=True)
def create_db_and_tables():
SQLModel.metadata.create_all(engine)
def create_heroes():
with Session(engine) as session:
team_preventers = Team(name="Preventers", headquarters="Sharp Tower")
team_z_force = Team(name="Z-Force", headquarters="Sister Margaret's Bar")
hero_deadpond = Hero(
name="Deadpond", secret_name="Dive Wilson", team=team_z_force
)
hero_rusty_man = Hero(
name="Rusty-Man", secret_name="Tommy Sharp", age=48, team=team_preventers
)
hero_spider_boy = Hero(name="Spider-Boy", secret_name="Pedro Parqueador")
session.add(hero_deadpond)
session.add(hero_rusty_man)
session.add(hero_spider_boy)
session.commit()
session.refresh(hero_deadpond)
session.refresh(hero_rusty_man)
session.refresh(hero_spider_boy)
print("Created hero:", hero_deadpond)
print("Created hero:", hero_rusty_man)
print("Created hero:", hero_spider_boy)
hero_spider_boy.team = team_preventers
session.add(hero_spider_boy)
session.commit()
session.refresh(hero_spider_boy)
print("Updated hero:", hero_spider_boy)
hero_black_lion = Hero(name="Black Lion", secret_name="Trevor Challa", age=35)
hero_sure_e = Hero(name="Princess Sure-E", secret_name="Sure-E")
team_wakaland = Team(
name="Wakaland",
headquarters="Wakaland Capital City",
heroes=[hero_black_lion, hero_sure_e],
)
session.add(team_wakaland)
session.commit()
session.refresh(team_wakaland)
print("Team Wakaland:", team_wakaland)
hero_tarantula = Hero(name="Tarantula", secret_name="Natalia Roman-on", age=32)
hero_dr_weird = Hero(name="Dr. Weird", secret_name="Steve Weird", age=36)
hero_cap = Hero(
name="Captain North America", secret_name="Esteban Rogelios", age=93
)
team_preventers.heroes.append(hero_tarantula)
team_preventers.heroes.append(hero_dr_weird)
team_preventers.heroes.append(hero_cap)
session.add(team_preventers)
session.commit()
session.refresh(hero_tarantula)
session.refresh(hero_dr_weird)
session.refresh(hero_cap)
print("Preventers new hero:", hero_tarantula)
print("Preventers new hero:", hero_dr_weird)
print("Preventers new hero:", hero_cap)
def select_heroes():
with Session(engine) as session:
statement = select(Team).where(Team.name == "Preventers")
result = session.exec(statement)
team_preventers = result.one()
print("Preventers heroes:", team_preventers.heroes)
def update_heroes():
with Session(engine) as session:
statement = select(Hero).where(Hero.name == "Spider-Boy")
result = session.exec(statement)
hero_spider_boy = result.one()
hero_spider_boy.team = None
session.add(hero_spider_boy)
session.commit()
session.refresh(hero_spider_boy)
print("Spider-Boy without team:", hero_spider_boy)
def main():
create_db_and_tables()
create_heroes()
select_heroes()
update_heroes()
if __name__ == "__main__":
main()
그리고 당연히, 이 update_heroes() 함수를 main()에 추가해서 커맨드라인에서 이 프로그램을 호출할 때 실행되도록 하는 걸 기억해야 해요:
# Code above omitted 👆
def main():
create_db_and_tables()
create_heroes()
select_heroes()
update_heroes()
# Code below omitted 👇
정리
이번 장은 정리할 게 너무 짧았죠? 🤔
어쨌든, 관계 속성은 데이터베이스에 저장된 관계를 쉽고 직관적으로 다루게 해 줘요. 🎉