Настройка для ORM Queryguide: Единое наследование¶
На этой странице показаны отображения и данные приспособлений, используемые в примерах Наследование одной таблицы в документе Написание операторов SELECT для отображений наследования Руководство по составлению запросов в ORM.
>>> from sqlalchemy import create_engine
>>> from sqlalchemy import ForeignKey
>>> from sqlalchemy.orm import DeclarativeBase
>>> from sqlalchemy.orm import Mapped
>>> from sqlalchemy.orm import mapped_column
>>> from sqlalchemy.orm import relationship
>>> from sqlalchemy.orm import Session
>>>
>>>
>>> class Base(DeclarativeBase):
... pass
>>> class Employee(Base):
... __tablename__ = "employee"
... id: Mapped[int] = mapped_column(primary_key=True)
... name: Mapped[str]
... type: Mapped[str]
...
... def __repr__(self):
... return f"{self.__class__.__name__}({self.name!r})"
...
... __mapper_args__ = {
... "polymorphic_identity": "employee",
... "polymorphic_on": "type",
... }
>>> class Manager(Employee):
... manager_name: Mapped[str] = mapped_column(nullable=True)
... __mapper_args__ = {
... "polymorphic_identity": "manager",
... }
>>> class Engineer(Employee):
... engineer_info: Mapped[str] = mapped_column(nullable=True)
... __mapper_args__ = {
... "polymorphic_identity": "engineer",
... }
>>>
>>> engine = create_engine("sqlite://", echo=True)
>>>
>>> Base.metadata.create_all(engine)
BEGIN ...
>>> conn = engine.connect()
>>> from sqlalchemy.orm import Session
>>> session = Session(conn)
>>> session.add_all(
... [
... Manager(
... name="Mr. Krabs",
... manager_name="Eugene H. Krabs",
... ),
... Engineer(name="SpongeBob", engineer_info="Krabby Patty Master"),
... Engineer(
... name="Squidward",
... engineer_info="Senior Customer Engagement Engineer",
... ),
... ],
... )
>>> session.commit()
BEGIN ...