Essential SQLAlchemy: Chapter 7

Essential-SQLAlchemy-2nd.org

@@ -4286,3 +4286,581 @@ Table(
   session.add(o2)
   session.commit()
 #+END_SRC
+
+*** Joins
+#+BEGIN_SRC python :results table
+  query = (
+      session.query(
+          Order.order_id,
+          User.username,
+          User.phone,
+          Cookie.cookie_name,
+          LineItem.quantity,
+          LineItem.extended_cost,
+      )
+      .join(User)
+      .join(LineItem)
+      .join(Cookie)
+      .filter(User.username == "cookiemon")
+  )
+  [row for row in query]
+#+END_SRC
+
+#+RESULTS[d7ab85e9d62ece5505b9bb871b863547945e9a2f]:
+| 1 | cookiemon | 111-111-1111 | chocolate chip |  2 | Decimal | (1.00) |
+| 1 | cookiemon | 111-111-1111 | peanut butter  | 12 | Decimal | (3.00) |
+
+*** Grouping
+#+BEGIN_SRC python :results table
+  query = (
+      session.query(User.username, func.count(Order.order_id))
+      .outerjoin(Order)
+      .group_by(User.username)
+      .all()
+  )
+  query
+#+END_SRC
+
+#+RESULTS[0654ad9c5fb1050dbb7fe12359ee0129d974cbec]:
+| cakeeater | 1 |
+| cookiemon | 1 |
+| pieperson | 0 |
+
+*** Chaining
+#+BEGIN_SRC python :results table
+  def get_orders_by_customer(
+      cust_name: str, shipped: bool | None = None, details: bool = False
+  ):
+      query = session.query(Order.order_id, User.username, User.phone).join(User)
+      if details:
+          query = query.add_columns(
+              Cookie.cookie_name, LineItem.quantity, LineItem.extended_cost
+          )
+          query = query.join(LineItem).join(Cookie)
+      if shipped is not None:
+          query = query.where(Order.shipped == shipped)
+      results = query.filter(User.username == cust_name).all()
+      return results
+
+
+  get_orders_by_customer("cakeeater")
+#+END_SRC
+
+#+RESULTS[2bfd4ed6da2da0894cbfff4533e06629a86a5409]:
+| 2 | cakeeater | 222-222-2222 |
+
+#+BEGIN_SRC python :results table
+  get_orders_by_customer("cakeeater", details=True)
+#+END_SRC
+
+#+RESULTS[a16214b5f672ae8f06d8fb0d3455914cc246b4c4]:
+| 2 | cakeeater | 222-222-2222 | chocolate chip | 24 | Decimal | (12.00) |
+| 2 | cakeeater | 222-222-2222 | oatmeal raisin |  6 | Decimal | (6.00)  |
+
+#+BEGIN_SRC python :results raw
+  get_orders_by_customer("cakeeater", shipped=True)
+#+END_SRC
+
+#+RESULTS[17638e98cd1333daa06557954f633699643c838f]:
+[]
+
+#+BEGIN_SRC python :results table
+  get_orders_by_customer("cakeeater", shipped=False)
+#+END_SRC
+
+#+RESULTS[9d1b1a41a3b45c33583ae66a399a093ff312b571]:
+| 2 | cakeeater | 222-222-2222 |
+
+#+BEGIN_SRC python :results table
+  get_orders_by_customer("cakeeater", shipped=False, details=True)
+#+END_SRC
+
+#+RESULTS[39653887c276c6a3e1d1a3715346a01c5abd6cba]:
+| 2 | cakeeater | 222-222-2222 | chocolate chip | 24 | Decimal | (12.00) |
+| 2 | cakeeater | 222-222-2222 | oatmeal raisin |  6 | Decimal | (6.00)  |
+
+
+*** Raw Queries
+#+BEGIN_SRC python :results output
+  from sqlalchemy import text
+  query = session.query(User).filter(text("username='cookiemon'"))
+  for u in query.all():
+      print(u)
+#+END_SRC
+
+#+RESULTS[93012273f06378bfd99097513d3d305cd839c551]:
+: User(
+:     user_id="1",
+:     username="cookiemon",
+:     email_address="mon@cookie.com",
+:     phone="111-111-1111",
+:     password="password",
+:     created_on="2026-09-21 10:55:18.029598",
+:     updated_on="2026-09-21 10:55:18.029607",
+: )
+
+** SQLAlchemy v2
+#+BEGIN_SRC python :tangle "ch7-v2.py" :shebang "#!/usr/bin/env python3" :results none
+  #!/usr/bin/env python3
+  """Идиоматичный SQLAlchemy 2.0 пример (по мотивам «Essential SQLAlchemy»)."""
+
+  import logging
+  import re
+  from datetime import datetime
+  from decimal import Decimal
+
+  import pandas as pd
+  from ruff_format import format_string
+  from sqlalchemy import (
+      Boolean,
+      DateTime,
+      ForeignKey,
+      Integer,
+      Numeric,
+      String,
+      create_engine,
+      delete,
+      func,
+      insert,
+      or_,
+      select,
+      text,
+      update,
+  )
+  from sqlalchemy.orm import (
+      DeclarativeBase,
+      Mapped,
+      Session,
+      mapped_column,
+      relationship,
+  )
+
+  # ---------------------------------------------------------------------------
+  # Engine
+  # ---------------------------------------------------------------------------
+  engine = create_engine("sqlite:///:memory:", echo=False)
+
+
+  # ---------------------------------------------------------------------------
+  # Базовый класс с удобным repr и display
+  # ---------------------------------------------------------------------------
+  class Base(DeclarativeBase):
+      """Базовый класс с repr() и display() для схемы таблицы."""
+
+      def __repr__(self) -> str:
+          raw = f"{self.__class__.__name__}"
+          columns = ",".join(
+              f"{col.name}={getattr(self, col.name)!r}"
+              for col in self.__table__.columns
+          )
+          return format_string(f"{raw}({columns})")
+
+      @classmethod
+      def display(cls) -> str:
+          raw = repr(cls.__table__).replace(
+              f"<{cls.__tablename__}>", f'"{cls.__tablename__}"'
+          )
+          raw = re.sub(
+              r"CallableColumnDefault\(<function datetime\.now at 0x[0-9a-f]+>\)",
+              "NOW",
+              raw,
+          )
+          try:
+              return format_string(raw)
+          except Exception:
+              logging.exception(raw)
+              return raw
+
+
+  # ---------------------------------------------------------------------------
+  # Модели
+  # ---------------------------------------------------------------------------
+  class Cookie(Base):
+      __tablename__ = "cookies"
+
+      cookie_id: Mapped[int] = mapped_column(primary_key=True)
+      cookie_name: Mapped[str | None] = mapped_column(String(50), index=True)
+      cookie_recipe_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))
+
+
+  class User(Base):
+      __tablename__ = "users"
+
+      user_id: Mapped[int] = mapped_column(primary_key=True)
+      username: Mapped[str] = mapped_column(String(12), nullable=False, unique=True)
+      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] = mapped_column(DateTime, default=datetime.now)
+      updated_on: Mapped[datetime] = mapped_column(
+          DateTime, default=datetime.now, onupdate=datetime.now
+      )
+
+
+  class Order(Base):
+      __tablename__ = "orders"
+
+      order_id: Mapped[int] = mapped_column(primary_key=True)
+      user_id: Mapped[int | None] = mapped_column(ForeignKey("users.user_id"))
+      shipped: Mapped[bool] = mapped_column(Boolean, default=False)
+
+      user: Mapped["User"] = relationship(back_populates="orders")
+      line_items: Mapped[list["LineItem"]] = relationship(back_populates="order")
+
+
+  class LineItem(Base):
+      __tablename__ = "line_items"
+
+      line_item_id: Mapped[int] = mapped_column(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))
+
+      order: Mapped["Order"] = relationship(back_populates="line_items")
+      cookie: Mapped["Cookie"] = relationship(uselist=False)
+
+
+  # Дополняем User.orders после объявления Order (back_populates с обеих сторон)
+  User.orders = relationship("Order", back_populates="user", order_by="Order.order_id")
+
+
+  # ---------------------------------------------------------------------------
+  # Создание схемы
+  # ---------------------------------------------------------------------------
+  Base.metadata.create_all(engine)
+
+  Cookie.display()
+  User.display()
+  Order.display()
+  LineItem.display()
+
+
+  # ---------------------------------------------------------------------------
+  # Работа с сессией
+  # ---------------------------------------------------------------------------
+  with Session(engine) as session:
+      # =======================================================================
+      # INSERT: одиночные объекты через ORM
+      # =======================================================================
+      cc_cookie = Cookie(
+          cookie_name="chocolate chip",
+          cookie_recipe_url="http://some.aweso.me/cookie/recipe.html",
+          cookie_sku="CC01",
+          quantity=12,
+          unit_cost=Decimal("0.50"),
+      )
+      session.add(cc_cookie)
+      session.commit()
+      print("cc_cookie.cookie_id =", cc_cookie.cookie_id)
+
+      dcc = Cookie(
+          cookie_name="dark chocolate chip",
+          cookie_recipe_url="http://some.aweso.me/cookie/recipe/recipe_dark.html",
+          cookie_sku="CC02",
+          quantity=1,
+          unit_cost=Decimal("0.75"),
+      )
+      mol = Cookie(
+          cookie_name="molasses",
+          cookie_recipe_url="http://some.aweso.me/cookie/recipe_molasses.html",
+          cookie_sku="MOL01",
+          quantity=1,
+          unit_cost=Decimal("0.80"),
+      )
+      session.add_all([dcc, mol])
+      session.flush()
+      print([("dcc.cookie_id", dcc.cookie_id), ("mol.cookie_id", mol.cookie_id)])
+
+      # =======================================================================
+      # INSERT: bulk-вставка (замена legacy bulk_save_objects)
+      # =======================================================================
+      session.execute(
+          insert(Cookie),
+          [
+              {
+                  "cookie_name": "peanut butter",
+                  "cookie_recipe_url": "http://some.aweso.me/cookie/recipe/peanut.html",
+                  "cookie_sku": "PB01",
+                  "quantity": 24,
+                  "unit_cost": Decimal("0.25"),
+              },
+              {
+                  "cookie_name": "oatmeal raisin",
+                  "cookie_recipe_url": "http://some.okay.me/cookie/raisin.html",
+                  "cookie_sku": "EWW01",
+                  "quantity": 100,
+                  "unit_cost": Decimal("1.00"),
+              },
+          ],
+      )
+      session.commit()
+
+      # Пример с .returning() — если нужны обратно PK/имена
+      result = session.execute(
+          insert(Cookie).returning(Cookie.cookie_id, Cookie.cookie_name),
+          [
+              {
+                  "cookie_name": "sugar",
+                  "cookie_recipe_url": "http://example.com/sugar",
+                  "cookie_sku": "SGR01",
+                  "quantity": 50,
+                  "unit_cost": Decimal("0.40"),
+              },
+          ],
+      )
+      print("inserted (returning):", result.all())
+      session.commit()
+
+      # =======================================================================
+      # SELECT: базовые
+      # =======================================================================
+      cookies = session.scalars(select(Cookie)).all()
+      print(cookies)
+
+      row = session.execute(select(Cookie.cookie_name, Cookie.quantity)).first()
+      print(row)
+
+      # =======================================================================
+      # DataFrame из select()
+      # =======================================================================
+      stmt = select(Cookie.quantity, Cookie.cookie_name).order_by(Cookie.quantity.desc())
+      rows = session.execute(stmt).all()
+      df = pd.DataFrame(rows, columns=["quantity", "cookie_name"])
+
+      headers = [""] + df.columns.tolist()
+      data_rows = [[idx, *row] for idx, row in zip(df.index, df.to_numpy().tolist())]
+      summary = [headers, None, *data_rows]
+      print(summary)
+
+      # =======================================================================
+      # LIMIT
+      # =======================================================================
+      stmt = select(Cookie).order_by(Cookie.quantity).limit(2)
+      print([(c.cookie_name,) for c in session.scalars(stmt)])
+
+      # =======================================================================
+      # Агрегаты
+      # =======================================================================
+      inv_count = session.scalar(select(func.sum(Cookie.quantity)))
+      print("inv_count =", inv_count)
+
+      rec = session.execute(
+          select(func.count(Cookie.cookie_name).label("inventory_count"))
+      ).one()
+      print((list(rec._mapping.keys()), (rec.inventory_count,)))
+
+      # =======================================================================
+      # Фильтры
+      # =======================================================================
+      record = session.scalars(
+          select(Cookie).where(Cookie.cookie_name == "chocolate chip")
+      ).first()
+      print(record)
+
+      record = session.scalars(
+          select(Cookie).filter_by(cookie_name="chocolate chip")
+      ).first()
+      print(record)
+
+      stmt = select(Cookie).where(Cookie.cookie_name.like("chocolate chip"))
+      print([c.cookie_name for c in session.scalars(stmt)])
+
+      # =======================================================================
+      # Вычисляемые колонки
+      # =======================================================================
+      stmt = select(Cookie.cookie_name, ("SKU-" + Cookie.cookie_sku).label("sku"))
+      for r in session.execute(stmt):
+          print(r)
+
+      stmt = select(
+          Cookie.cookie_name,
+          func.cast(Cookie.quantity * Cookie.unit_cost, Numeric(12, 2)).label("inv_cost"),
+      )
+      print([(r.cookie_name, repr(r.inv_cost)) for r in session.execute(stmt)])
+
+      stmt = select(Cookie).where(
+          Cookie.quantity > 23, Cookie.unit_cost < Decimal("0.40")
+      )
+      print([(c.cookie_name,) for c in session.scalars(stmt)])
+
+      stmt = select(Cookie).where(
+          or_(
+              Cookie.quantity.between(10, 50),
+              Cookie.cookie_name.contains("chip"),
+          )
+      )
+      print([(c.cookie_name,) for c in session.scalars(stmt)])
+
+      # =======================================================================
+      # UPDATE (ORM-объект)
+      # =======================================================================
+      cc_cookie = session.scalars(
+          select(Cookie).filter_by(cookie_name="chocolate chip")
+      ).first()
+      assert cc_cookie is not None
+      cc_cookie.quantity = (cc_cookie.quantity or 0) + 120
+      session.commit()
+      print("cc_cookie.quantity =", cc_cookie.quantity)
+
+      # UPDATE (bulk)
+      session.execute(
+          update(Cookie)
+          .where(Cookie.cookie_name == "chocolate chip")
+          .values(quantity=Cookie.quantity - 20)
+      )
+      session.commit()
+      print(
+          "after bulk update:",
+          session.scalars(
+              select(Cookie.quantity).where(Cookie.cookie_name == "chocolate chip")
+          ).one(),
+      )
+
+      # =======================================================================
+      # DELETE (ORM)
+      # =======================================================================
+      dcc_cookie = session.scalars(
+          select(Cookie).filter_by(cookie_name="dark chocolate chip")
+      ).one()
+      session.delete(dcc_cookie)
+      session.commit()
+      assert (
+          session.scalars(
+              select(Cookie).filter_by(cookie_name="dark chocolate chip")
+          ).first()
+          is None
+      )
+
+      # DELETE (bulk)
+      session.execute(delete(Cookie).where(Cookie.cookie_name == "molasses"))
+      session.commit()
+      assert (
+          session.scalars(select(Cookie).filter_by(cookie_name="molasses")).first()
+          is None
+      )
+
+      # =======================================================================
+      # Пользователи и связи
+      # =======================================================================
+      cookiemon = User(
+          username="cookiemon",
+          email_address="mon@cookie.com",
+          phone="111-111-1111",
+          password="password",
+      )
+      cakeeater = User(
+          username="cakeeater",
+          email_address="cakeeater@cake.com",
+          phone="222-222-2222",
+          password="password",
+      )
+      pieperson = User(
+          username="pieperson",
+          email_address="person@pie.com",
+          phone="333-333-3333",
+          password="password",
+      )
+      session.add_all([cookiemon, cakeeater, pieperson])
+      session.commit()
+
+      o1 = Order()
+      o1.user = cookiemon
+      session.add(o1)
+
+      cc = session.scalars(
+          select(Cookie).filter_by(cookie_name="chocolate chip")
+      ).one()
+      pb = session.scalars(
+          select(Cookie).filter_by(cookie_name="peanut butter")
+      ).one()
+
+      line1 = LineItem(cookie=cc, quantity=2, extended_cost=Decimal("1.00"))
+      line2 = LineItem(quantity=12, extended_cost=Decimal("3.00"))
+      line2.cookie = pb
+      line2.order = o1
+      o1.line_items.append(line1)
+      o1.line_items.append(line2)
+      session.commit()
+
+      o2 = Order()
+      o2.user = cakeeater
+      line1 = LineItem(cookie=cc, quantity=24, extended_cost=Decimal("12.00"))
+      oat = session.scalars(
+          select(Cookie).filter_by(cookie_name="oatmeal raisin")
+      ).one()
+      line2 = LineItem(cookie=oat, quantity=6, extended_cost=Decimal("6.00"))
+      o2.line_items.append(line1)
+      o2.line_items.append(line2)
+      session.add(o2)
+      session.commit()
+
+      # =======================================================================
+      # JOIN
+      # =======================================================================
+      stmt = (
+          select(
+              Order.order_id,
+              User.username,
+              User.phone,
+              Cookie.cookie_name,
+              LineItem.quantity,
+              LineItem.extended_cost,
+          )
+          .join(User)
+          .join(LineItem)
+          .join(Cookie)
+          .where(User.username == "cookiemon")
+      )
+      print([tuple(r) for r in session.execute(stmt)])
+
+      # =======================================================================
+      # GROUP BY + OUTER JOIN
+      # =======================================================================
+      stmt = (
+          select(User.username, func.count(Order.order_id))
+          .outerjoin(Order)
+          .group_by(User.username)
+      )
+      print(session.execute(stmt).all())
+
+      # =======================================================================
+      # Функция-обёртка
+      # =======================================================================
+      def get_orders_by_customer(
+          cust_name: str,
+          shipped: bool | None = None,
+          details: bool = False,
+      ):
+          stmt = select(Order.order_id, User.username, User.phone).join(User)
+          if details:
+              stmt = (
+                  stmt.add_columns(
+                      Cookie.cookie_name,
+                      LineItem.quantity,
+                      LineItem.extended_cost,
+                  )
+                  .join(LineItem)
+                  .join(Cookie)
+              )
+          if shipped is not None:
+              stmt = stmt.where(Order.shipped == shipped)
+          stmt = stmt.where(User.username == cust_name)
+          return session.execute(stmt).all()
+
+      print(get_orders_by_customer("cakeeater"))
+      print(get_orders_by_customer("cakeeater", details=True))
+      print(get_orders_by_customer("cakeeater", shipped=True))
+      print(get_orders_by_customer("cakeeater", shipped=False))
+      print(get_orders_by_customer("cakeeater", shipped=False, details=True))
+
+      # =======================================================================
+      # Текстовый SQL
+      # =======================================================================
+      stmt = select(User).where(text("username='cookiemon'"))
+      for u in session.scalars(stmt):
+          print(u)
+#+END_SRC