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:orphan:
======================================
Setup for ORM Queryguide: DML
======================================
This page illustrates the mappings and fixture data used by the
:doc:`dml` document of the :ref:`queryguide_toplevel`.
.. sourcecode:: python
>>> from typing import List
>>> from typing import Optional
>>> import datetime
>>>
>>> from sqlalchemy import Column
>>> from sqlalchemy import create_engine
>>> from sqlalchemy import ForeignKey
>>> from sqlalchemy import Table
>>> 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 User(Base):
... __tablename__ = "user_account"
... id: Mapped[int] = mapped_column(primary_key=True)
... name: Mapped[str] = mapped_column(unique=True)
... fullname: Mapped[Optional[str]]
... species: Mapped[Optional[str]]
... addresses: Mapped[List["Address"]] = relationship(back_populates="user")
...
... def __repr__(self) -> str:
... return f"User(name={self.name!r}, fullname={self.fullname!r})"
>>> class Address(Base):
... __tablename__ = "address"
... id: Mapped[int] = mapped_column(primary_key=True)
... user_id: Mapped[int] = mapped_column(ForeignKey("user_account.id"))
... email_address: Mapped[str]
... user: Mapped[User] = relationship(back_populates="addresses")
...
... def __repr__(self) -> str:
... return f"Address(email_address={self.email_address!r})"
>>> class LogRecord(Base):
... __tablename__ = "log_record"
... id: Mapped[int] = mapped_column(primary_key=True)
... message: Mapped[str]
... code: Mapped[str]
... timestamp: Mapped[datetime.datetime]
...
... def __repr__(self):
... return f"LogRecord({self.message!r}, {self.code!r}, {self.timestamp!r})"
>>> 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):
... __tablename__ = "manager"
... id: Mapped[int] = mapped_column(ForeignKey("employee.id"), primary_key=True)
... manager_name: Mapped[str]
...
... def __repr__(self):
... return f"{self.__class__.__name__}({self.name!r}, manager_name={self.manager_name!r})"
...
... __mapper_args__ = {
... "polymorphic_identity": "manager",
... }
>>> class Engineer(Employee):
... __tablename__ = "engineer"
... id: Mapped[int] = mapped_column(ForeignKey("employee.id"), primary_key=True)
... engineer_info: Mapped[str]
...
... def __repr__(self):
... return f"{self.__class__.__name__}({self.name!r}, engineer_info={self.engineer_info!r})"
...
... __mapper_args__ = {
... "polymorphic_identity": "engineer",
... }
>>> engine = create_engine("sqlite+pysqlite:///:memory:", echo=True)
>>> Base.metadata.create_all(engine)
BEGIN ...
>>> conn = engine.connect()
>>> session = Session(conn)
>>> conn.begin()
BEGIN ...
|
