sqlalchemy-alembic/Essential-SQLAlchemy-2nd.org

• Chapter 1: Schema and Types
  • SQLAlchemy v1
  • SQLAlchemy v2

Chapter 1: Schema and Types

SQLAlchemy v1

  import sqlalchemy
  print(sqlalchemy.__version__)

2.0.52

  from sqlalchemy import MetaData

  metadata = MetaData()

  from sqlalchemy import Table, Column, Integer, Numeric, String, CheckConstraint

  cookies = Table(
      "cookies",
      metadata,
      Column("cookie_id", Integer(), primary_key=True),
      Column("cookie_name", String(50), index=True),
      Column("cookie_recipie_url", String(255)),
      Column("cookie_sku", String(55)),
      Column("quantity", Integer()),
      Column("unit_cost", Numeric(12, 2)),
      CheckConstraint("unit_cost >= 0.00", name="unit_cost_positive"),
  )

  from datetime import datetime
  from sqlalchemy import DateTime, PrimaryKeyConstraint, UniqueConstraint

  users = Table(
      "users",
      metadata,
      Column("user_id", Integer()),
      Column("username", String(15), nullable=False),
      Column("email_address", String(255), nullable=False),
      Column("phone", String(20), nullable=False),
      Column("password", String(25), nullable=False),
      Column("created_on", DateTime(), default=datetime.now),
      Column("updated_on", DateTime(), default=datetime.now, onupdate=datetime.now),
      PrimaryKeyConstraint("user_id", name="user_pk"),
      UniqueConstraint("username", name="uix_username"),
  )

  @startuml
  skinparam linetype ortho
  skinparam nodesep 30
  skinparam ranksep 40

  skinparam entity {
  	BackgroundColor White
  	BorderColor Black
  	BorderThickness 1.2
  	FontStyle bold
  	FontSize 12
  }

  entity orders {
  	,**order_id** : PK
  	--
  	user_id : FK
  }
  entity line_items {
  	,**line_item_id**: PK
  	--
  	,**order_id** : FK
  	,**cookie_id** : FK
  	quantity
  	extended_cost
  }
  entity cookies {
  	,**cookie_id** : PK
  	--
  	cookie_name
  	cookie_reciepe_url
  	cookie_sku
  	quantity
  	unit_cost
  }
  entity users {
  	,**user_id** : PK
  	--
  	customer_number
  	username
  	email-address
  	phone
  	password
  	created_on
  	updated_on
  }

  orders ||--|{ line_items
  line_items }o--|| cookies
  orders }o--|| users

  orders -[hidden]right- line_items
  line_items -[hidden]right- cookies
  orders -[hidden]down- users
  @enduml

  from sqlalchemy import ForeignKey, Boolean

  orders = Table(
      "orders",
      metadata,
      Column("order_id", Integer(), primary_key=True),
      Column("user_id", ForeignKey("users.user_id")),
      Column("shipped", Boolean(), default=False),
  )


  line_items = Table(
      "line_items",
      metadata,
      Column("line_items_id", Integer(), primary_key=True),
      Column("order_id", ForeignKey("orders.order_id")),
      Column("cookie_id", ForeignKey("cookies.cookie_id")),
      Column("quantity", Integer()),
      Column("extended_cost", Numeric(12, 2)),
  )

  <<A1>>
  <<B1>>
  <<C1>>
  <<D1>>
  from sqlalchemy import create_engine

  engine = create_engine("sqlite:///:memory:", echo=True)
  metadata.create_all(engine)

SQLAlchemy v2

  #!/usr/bin/env python3
  from datetime import datetime
  from decimal import Decimal

  from sqlalchemy import (
      Boolean,
      CheckConstraint,
      DateTime,
      ForeignKey,
      Integer,
      Numeric,
      String,
      UniqueConstraint,
      create_engine,
  )
  from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column, relationship


  class Base(DeclarativeBase):
      """Базовый класс для всех ORM-моделей."""


  class Cookie(Base):
      __tablename__ = "cookies"

      cookie_id: Mapped[int] = mapped_column(Integer, primary_key=True)
      cookie_name: Mapped[str | None] = mapped_column(String(50), index=True)
      cookie_recipie_url: Mapped[str | None] = mapped_column(String(255))
      cookie_sku: Mapped[str | None] = mapped_column(String(55))
      quantity: Mapped[int | None] = mapped_column(Integer)
      unit_cost: Mapped[Decimal | None] = mapped_column(Numeric(12, 2))

      __table_args__ = (CheckConstraint("unit_cost >= 0.00", name="unit_cost_positive"),)

      # Связь: одна cookie -> много line_items
      line_items: Mapped[list["LineItem"]] = relationship(back_populates="cookie")

      def __repr__(self) -> str:
          return f"Cookie(cookie_id={self.cookie_id!r}, cookie_name={self.cookie_name!r})"


  class User(Base):
      __tablename__ = "users"

      user_id: Mapped[int] = mapped_column(Integer, primary_key=True)
      username: Mapped[str] = mapped_column(String(15), nullable=False)
      email_address: Mapped[str] = mapped_column(String(255), nullable=False)
      phone: Mapped[str] = mapped_column(String(20), nullable=False)
      password: Mapped[str] = mapped_column(String(25), nullable=False)
      created_on: Mapped[datetime | None] = mapped_column(DateTime, default=datetime.now)
      updated_on: Mapped[datetime | None] = mapped_column(
          DateTime, default=datetime.now, onupdate=datetime.now
      )

      __table_args__ = (UniqueConstraint("username", name="uix_username"),)

      # Связь: один user -> много orders
      orders: Mapped[list["Order"]] = relationship(back_populates="user")

      def __repr__(self) -> str:
          return f"User(user_id={self.user_id!r}, username={self.username!r})"


  class Order(Base):
      __tablename__ = "orders"

      order_id: Mapped[int] = mapped_column(Integer, primary_key=True)
      user_id: Mapped[int | None] = mapped_column(ForeignKey("users.user_id"))
      shipped: Mapped[bool | None] = mapped_column(Boolean, default=False)

      # Связи
      user: Mapped["User | None"] = relationship(back_populates="orders")
      line_items: Mapped[list["LineItem"]] = relationship(back_populates="order")

      def __repr__(self) -> str:
          return f"Order(order_id={self.order_id!r}, user_id={self.user_id!r})"


  class LineItem(Base):
      __tablename__ = "line_items"

      line_items_id: Mapped[int] = mapped_column(Integer, primary_key=True)
      order_id: Mapped[int | None] = mapped_column(ForeignKey("orders.order_id"))
      cookie_id: Mapped[int | None] = mapped_column(ForeignKey("cookies.cookie_id"))
      quantity: Mapped[int | None] = mapped_column(Integer)
      extended_cost: Mapped[Decimal | None] = mapped_column(Numeric(12, 2))

      # Связи
      order: Mapped["Order | None"] = relationship(back_populates="line_items")
      cookie: Mapped["Cookie | None"] = relationship(back_populates="line_items")

      def __repr__(self) -> str:
          return (
              f"LineItem(line_items_id={self.line_items_id!r}, "
              f"order_id={self.order_id!r}, cookie_id={self.cookie_id!r})"
          )


  if __name__ == "__main__":
      engine = create_engine("sqlite:///:memory:", echo=True)
      Base.metadata.create_all(engine)