SQLAlchemy Essential: Chapter 1
This commit is contained in:
Pavel Vavilin
@@ -1,4 +1,6 @@
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* Chapter 1: Schema and Types
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** SQLAlchemy v1
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#+BEGIN_SRC python :results output
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import sqlalchemy
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print(sqlalchemy.__version__)
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@@ -7,16 +9,17 @@
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#+RESULTS:
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: 2.0.52
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#+BEGIN_SRC python :session ch1
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#+NAME: A1
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#+BEGIN_SRC python :session ch1 :results none
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from sqlalchemy import MetaData
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metadata = MetaData()
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#+END_SRC
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#+BEGIN_SRC python :session ch1
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from sqlalchemy import Table, Column, Integer, Numeric, String, ForeignKey
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#+NAME: B1
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#+BEGIN_SRC python :session ch1 :results none
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from sqlalchemy import Table, Column, Integer, Numeric, String, CheckConstraint
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cookies = Table(
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"cookies",
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@@ -27,22 +30,229 @@
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Column("cookie_sku", String(55)),
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Column("quantity", Integer()),
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Column("unit_cost", Numeric(12, 2)),
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CheckConstraint("unit_cost >= 0.00", name="unit_cost_positive"),
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)
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#+END_SRC
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#+BEGIN_SRC python :session ch1
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#+NAME: C1
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#+BEGIN_SRC python :session ch1 :results none
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from datetime import datetime
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from sqlalchemy import DateTime
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from sqlalchemy import DateTime, PrimaryKeyConstraint, UniqueConstraint
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users = Table(
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"users",
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metadata,
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Column("user_id", Integer(), primary_key=True),
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Column("username", String(15), nullable=False, unique=True),
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Column("user_id", Integer()),
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Column("username", String(15), nullable=False),
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Column("email_address", String(255), nullable=False),
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Column("phone", String(20), nullable=False),
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Column("password", String(25), nullable=False),
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Column("created_on", DateTime(), default=datetime.now),
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Column("updated_on", DateTime(), default=datetime.now, onupdate=datetime.now),
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PrimaryKeyConstraint("user_id", name="user_pk"),
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UniqueConstraint("username", name="uix_username"),
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)
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#+END_SRC
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#+BEGIN_SRC plantuml :file er.png
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@startuml
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skinparam linetype ortho
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skinparam nodesep 30
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skinparam ranksep 40
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skinparam entity {
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BackgroundColor White
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BorderColor Black
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BorderThickness 1.2
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FontStyle bold
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FontSize 12
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}
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entity orders {
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,**order_id** : PK
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--
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user_id : FK
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}
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entity line_items {
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,**line_item_id**: PK
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--
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,**order_id** : FK
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,**cookie_id** : FK
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quantity
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extended_cost
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}
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entity cookies {
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,**cookie_id** : PK
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--
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cookie_name
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cookie_reciepe_url
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cookie_sku
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quantity
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unit_cost
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}
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entity users {
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,**user_id** : PK
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--
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customer_number
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username
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email-address
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phone
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password
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created_on
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updated_on
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}
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orders ||--|{ line_items
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line_items }o--|| cookies
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orders }o--|| users
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orders -[hidden]right- line_items
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line_items -[hidden]right- cookies
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orders -[hidden]down- users
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@enduml
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#+END_SRC
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#+RESULTS:
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[[file:er.png]]
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#+NAME: D1
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#+BEGIN_SRC python :session ch1 :results none
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from sqlalchemy import ForeignKey, Boolean
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orders = Table(
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"orders",
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metadata,
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Column("order_id", Integer(), primary_key=True),
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Column("user_id", ForeignKey("users.user_id")),
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Column("shipped", Boolean(), default=False),
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)
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line_items = Table(
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"line_items",
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metadata,
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Column("line_items_id", Integer(), primary_key=True),
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Column("order_id", ForeignKey("orders.order_id")),
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Column("cookie_id", ForeignKey("cookies.cookie_id")),
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Column("quantity", Integer()),
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Column("extended_cost", Numeric(12, 2)),
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)
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#+END_SRC
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#+NAME: E1
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#+BEGIN_SRC python :session ch1 :results none :tangle ch1-v1.py :noweb tangle :shebang "#!/usr/bin/env python3"
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<<A1>>
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<<B1>>
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<<C1>>
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<<D1>>
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from sqlalchemy import create_engine
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engine = create_engine("sqlite:///:memory:", echo=True)
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metadata.create_all(engine)
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#+END_SRC
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** SQLAlchemy v2
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#+BEGIN_SRC python :results none :tangle ch1-v2.py :noweb tangle :shebang "#!/usr/bin/env python3"
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#!/usr/bin/env python3
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from datetime import datetime
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from decimal import Decimal
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from sqlalchemy import (
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Boolean,
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CheckConstraint,
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DateTime,
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ForeignKey,
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Integer,
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Numeric,
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String,
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UniqueConstraint,
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create_engine,
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)
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from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column, relationship
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class Base(DeclarativeBase):
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"""Базовый класс для всех ORM-моделей."""
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class Cookie(Base):
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__tablename__ = "cookies"
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cookie_id: Mapped[int] = mapped_column(Integer, primary_key=True)
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cookie_name: Mapped[str | None] = mapped_column(String(50), index=True)
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cookie_recipie_url: Mapped[str | None] = mapped_column(String(255))
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cookie_sku: Mapped[str | None] = mapped_column(String(55))
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quantity: Mapped[int | None] = mapped_column(Integer)
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unit_cost: Mapped[Decimal | None] = mapped_column(Numeric(12, 2))
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__table_args__ = (CheckConstraint("unit_cost >= 0.00", name="unit_cost_positive"),)
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# Связь: одна cookie -> много line_items
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line_items: Mapped[list["LineItem"]] = relationship(back_populates="cookie")
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def __repr__(self) -> str:
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return f"Cookie(cookie_id={self.cookie_id!r}, cookie_name={self.cookie_name!r})"
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class User(Base):
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__tablename__ = "users"
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user_id: Mapped[int] = mapped_column(Integer, primary_key=True)
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username: Mapped[str] = mapped_column(String(15), nullable=False)
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email_address: Mapped[str] = mapped_column(String(255), nullable=False)
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phone: Mapped[str] = mapped_column(String(20), nullable=False)
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password: Mapped[str] = mapped_column(String(25), nullable=False)
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created_on: Mapped[datetime | None] = mapped_column(DateTime, default=datetime.now)
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updated_on: Mapped[datetime | None] = mapped_column(
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DateTime, default=datetime.now, onupdate=datetime.now
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)
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__table_args__ = (UniqueConstraint("username", name="uix_username"),)
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# Связь: один user -> много orders
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orders: Mapped[list["Order"]] = relationship(back_populates="user")
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def __repr__(self) -> str:
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return f"User(user_id={self.user_id!r}, username={self.username!r})"
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class Order(Base):
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__tablename__ = "orders"
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order_id: Mapped[int] = mapped_column(Integer, primary_key=True)
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user_id: Mapped[int | None] = mapped_column(ForeignKey("users.user_id"))
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shipped: Mapped[bool | None] = mapped_column(Boolean, default=False)
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# Связи
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user: Mapped["User | None"] = relationship(back_populates="orders")
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line_items: Mapped[list["LineItem"]] = relationship(back_populates="order")
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def __repr__(self) -> str:
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return f"Order(order_id={self.order_id!r}, user_id={self.user_id!r})"
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class LineItem(Base):
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__tablename__ = "line_items"
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line_items_id: Mapped[int] = mapped_column(Integer, primary_key=True)
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order_id: Mapped[int | None] = mapped_column(ForeignKey("orders.order_id"))
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cookie_id: Mapped[int | None] = mapped_column(ForeignKey("cookies.cookie_id"))
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quantity: Mapped[int | None] = mapped_column(Integer)
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extended_cost: Mapped[Decimal | None] = mapped_column(Numeric(12, 2))
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# Связи
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order: Mapped["Order | None"] = relationship(back_populates="line_items")
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cookie: Mapped["Cookie | None"] = relationship(back_populates="line_items")
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def __repr__(self) -> str:
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return (
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f"LineItem(line_items_id={self.line_items_id!r}, "
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f"order_id={self.order_id!r}, cookie_id={self.cookie_id!r})"
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)
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if __name__ == "__main__":
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engine = create_engine("sqlite:///:memory:", echo=True)
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Base.metadata.create_all(engine)
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#+END_SRC
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