Essential SQLAlchemy: Chapter 7
This commit is contained in:
Pavel Vavilin
@@ -4286,3 +4286,581 @@ Table(
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session.add(o2)
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session.commit()
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#+END_SRC
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*** Joins
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#+BEGIN_SRC python :results table
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query = (
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session.query(
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Order.order_id,
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User.username,
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User.phone,
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Cookie.cookie_name,
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LineItem.quantity,
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LineItem.extended_cost,
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)
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.join(User)
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.join(LineItem)
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.join(Cookie)
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.filter(User.username == "cookiemon")
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)
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[row for row in query]
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#+END_SRC
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#+RESULTS[d7ab85e9d62ece5505b9bb871b863547945e9a2f]:
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| 1 | cookiemon | 111-111-1111 | chocolate chip | 2 | Decimal | (1.00) |
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| 1 | cookiemon | 111-111-1111 | peanut butter | 12 | Decimal | (3.00) |
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*** Grouping
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#+BEGIN_SRC python :results table
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query = (
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session.query(User.username, func.count(Order.order_id))
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.outerjoin(Order)
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.group_by(User.username)
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.all()
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)
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query
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#+END_SRC
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#+RESULTS[0654ad9c5fb1050dbb7fe12359ee0129d974cbec]:
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| cakeeater | 1 |
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| cookiemon | 1 |
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| pieperson | 0 |
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*** Chaining
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#+BEGIN_SRC python :results table
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def get_orders_by_customer(
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cust_name: str, shipped: bool | None = None, details: bool = False
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):
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query = session.query(Order.order_id, User.username, User.phone).join(User)
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if details:
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query = query.add_columns(
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Cookie.cookie_name, LineItem.quantity, LineItem.extended_cost
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)
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query = query.join(LineItem).join(Cookie)
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if shipped is not None:
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query = query.where(Order.shipped == shipped)
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results = query.filter(User.username == cust_name).all()
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return results
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get_orders_by_customer("cakeeater")
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#+END_SRC
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#+RESULTS[2bfd4ed6da2da0894cbfff4533e06629a86a5409]:
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| 2 | cakeeater | 222-222-2222 |
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#+BEGIN_SRC python :results table
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get_orders_by_customer("cakeeater", details=True)
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#+END_SRC
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#+RESULTS[a16214b5f672ae8f06d8fb0d3455914cc246b4c4]:
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| 2 | cakeeater | 222-222-2222 | chocolate chip | 24 | Decimal | (12.00) |
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| 2 | cakeeater | 222-222-2222 | oatmeal raisin | 6 | Decimal | (6.00) |
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#+BEGIN_SRC python :results raw
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get_orders_by_customer("cakeeater", shipped=True)
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#+END_SRC
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#+RESULTS[17638e98cd1333daa06557954f633699643c838f]:
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[]
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#+BEGIN_SRC python :results table
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get_orders_by_customer("cakeeater", shipped=False)
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#+END_SRC
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#+RESULTS[9d1b1a41a3b45c33583ae66a399a093ff312b571]:
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| 2 | cakeeater | 222-222-2222 |
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#+BEGIN_SRC python :results table
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get_orders_by_customer("cakeeater", shipped=False, details=True)
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#+END_SRC
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#+RESULTS[39653887c276c6a3e1d1a3715346a01c5abd6cba]:
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| 2 | cakeeater | 222-222-2222 | chocolate chip | 24 | Decimal | (12.00) |
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| 2 | cakeeater | 222-222-2222 | oatmeal raisin | 6 | Decimal | (6.00) |
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*** Raw Queries
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#+BEGIN_SRC python :results output
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from sqlalchemy import text
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query = session.query(User).filter(text("username='cookiemon'"))
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for u in query.all():
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print(u)
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#+END_SRC
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#+RESULTS[93012273f06378bfd99097513d3d305cd839c551]:
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: User(
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: user_id="1",
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: username="cookiemon",
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: email_address="mon@cookie.com",
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: phone="111-111-1111",
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: password="password",
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: created_on="2026-09-21 10:55:18.029598",
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: updated_on="2026-09-21 10:55:18.029607",
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: )
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** SQLAlchemy v2
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#+BEGIN_SRC python :tangle "ch7-v2.py" :shebang "#!/usr/bin/env python3" :results none
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#!/usr/bin/env python3
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"""Идиоматичный SQLAlchemy 2.0 пример (по мотивам «Essential SQLAlchemy»)."""
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import logging
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import re
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from datetime import datetime
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from decimal import Decimal
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import pandas as pd
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from ruff_format import format_string
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from sqlalchemy import (
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Boolean,
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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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create_engine,
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delete,
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func,
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insert,
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or_,
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select,
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text,
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update,
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)
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from sqlalchemy.orm import (
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DeclarativeBase,
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Mapped,
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Session,
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mapped_column,
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relationship,
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)
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# ---------------------------------------------------------------------------
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# Engine
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# ---------------------------------------------------------------------------
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engine = create_engine("sqlite:///:memory:", echo=False)
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# ---------------------------------------------------------------------------
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# Базовый класс с удобным repr и display
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# ---------------------------------------------------------------------------
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class Base(DeclarativeBase):
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"""Базовый класс с repr() и display() для схемы таблицы."""
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def __repr__(self) -> str:
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raw = f"{self.__class__.__name__}"
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columns = ",".join(
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f"{col.name}={getattr(self, col.name)!r}"
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for col in self.__table__.columns
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)
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return format_string(f"{raw}({columns})")
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@classmethod
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def display(cls) -> str:
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raw = repr(cls.__table__).replace(
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f"<{cls.__tablename__}>", f'"{cls.__tablename__}"'
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)
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raw = re.sub(
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r"CallableColumnDefault\(<function datetime\.now at 0x[0-9a-f]+>\)",
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"NOW",
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raw,
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)
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try:
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return format_string(raw)
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except Exception:
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logging.exception(raw)
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return raw
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# ---------------------------------------------------------------------------
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# Модели
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# ---------------------------------------------------------------------------
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class Cookie(Base):
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__tablename__ = "cookies"
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cookie_id: Mapped[int] = mapped_column(primary_key=True)
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cookie_name: Mapped[str | None] = mapped_column(String(50), index=True)
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cookie_recipe_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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class User(Base):
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__tablename__ = "users"
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user_id: Mapped[int] = mapped_column(primary_key=True)
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username: Mapped[str] = mapped_column(String(12), nullable=False, unique=True)
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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] = mapped_column(DateTime, default=datetime.now)
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updated_on: Mapped[datetime] = mapped_column(
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DateTime, default=datetime.now, onupdate=datetime.now
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)
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class Order(Base):
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__tablename__ = "orders"
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order_id: Mapped[int] = mapped_column(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] = mapped_column(Boolean, default=False)
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user: Mapped["User"] = relationship(back_populates="orders")
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line_items: Mapped[list["LineItem"]] = relationship(back_populates="order")
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class LineItem(Base):
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__tablename__ = "line_items"
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line_item_id: Mapped[int] = mapped_column(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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order: Mapped["Order"] = relationship(back_populates="line_items")
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cookie: Mapped["Cookie"] = relationship(uselist=False)
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# Дополняем User.orders после объявления Order (back_populates с обеих сторон)
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User.orders = relationship("Order", back_populates="user", order_by="Order.order_id")
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# ---------------------------------------------------------------------------
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# Создание схемы
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# ---------------------------------------------------------------------------
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Base.metadata.create_all(engine)
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Cookie.display()
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User.display()
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Order.display()
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LineItem.display()
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# ---------------------------------------------------------------------------
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# Работа с сессией
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# ---------------------------------------------------------------------------
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with Session(engine) as session:
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# =======================================================================
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# INSERT: одиночные объекты через ORM
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# =======================================================================
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cc_cookie = Cookie(
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cookie_name="chocolate chip",
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cookie_recipe_url="http://some.aweso.me/cookie/recipe.html",
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cookie_sku="CC01",
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quantity=12,
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unit_cost=Decimal("0.50"),
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)
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session.add(cc_cookie)
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session.commit()
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print("cc_cookie.cookie_id =", cc_cookie.cookie_id)
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dcc = Cookie(
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cookie_name="dark chocolate chip",
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cookie_recipe_url="http://some.aweso.me/cookie/recipe/recipe_dark.html",
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cookie_sku="CC02",
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quantity=1,
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unit_cost=Decimal("0.75"),
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)
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mol = Cookie(
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cookie_name="molasses",
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cookie_recipe_url="http://some.aweso.me/cookie/recipe_molasses.html",
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cookie_sku="MOL01",
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quantity=1,
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unit_cost=Decimal("0.80"),
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)
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session.add_all([dcc, mol])
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session.flush()
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print([("dcc.cookie_id", dcc.cookie_id), ("mol.cookie_id", mol.cookie_id)])
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# =======================================================================
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# INSERT: bulk-вставка (замена legacy bulk_save_objects)
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# =======================================================================
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session.execute(
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insert(Cookie),
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[
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{
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"cookie_name": "peanut butter",
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"cookie_recipe_url": "http://some.aweso.me/cookie/recipe/peanut.html",
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"cookie_sku": "PB01",
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"quantity": 24,
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"unit_cost": Decimal("0.25"),
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},
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{
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"cookie_name": "oatmeal raisin",
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"cookie_recipe_url": "http://some.okay.me/cookie/raisin.html",
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"cookie_sku": "EWW01",
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"quantity": 100,
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"unit_cost": Decimal("1.00"),
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},
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],
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)
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session.commit()
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# Пример с .returning() — если нужны обратно PK/имена
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result = session.execute(
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insert(Cookie).returning(Cookie.cookie_id, Cookie.cookie_name),
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[
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{
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"cookie_name": "sugar",
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"cookie_recipe_url": "http://example.com/sugar",
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"cookie_sku": "SGR01",
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"quantity": 50,
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"unit_cost": Decimal("0.40"),
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},
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],
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)
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print("inserted (returning):", result.all())
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session.commit()
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# =======================================================================
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# SELECT: базовые
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# =======================================================================
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cookies = session.scalars(select(Cookie)).all()
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print(cookies)
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row = session.execute(select(Cookie.cookie_name, Cookie.quantity)).first()
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print(row)
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# =======================================================================
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# DataFrame из select()
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# =======================================================================
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stmt = select(Cookie.quantity, Cookie.cookie_name).order_by(Cookie.quantity.desc())
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rows = session.execute(stmt).all()
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df = pd.DataFrame(rows, columns=["quantity", "cookie_name"])
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headers = [""] + df.columns.tolist()
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data_rows = [[idx, *row] for idx, row in zip(df.index, df.to_numpy().tolist())]
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summary = [headers, None, *data_rows]
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print(summary)
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# =======================================================================
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# LIMIT
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# =======================================================================
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stmt = select(Cookie).order_by(Cookie.quantity).limit(2)
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print([(c.cookie_name,) for c in session.scalars(stmt)])
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# =======================================================================
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# Агрегаты
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# =======================================================================
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inv_count = session.scalar(select(func.sum(Cookie.quantity)))
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print("inv_count =", inv_count)
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rec = session.execute(
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select(func.count(Cookie.cookie_name).label("inventory_count"))
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).one()
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print((list(rec._mapping.keys()), (rec.inventory_count,)))
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# =======================================================================
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# Фильтры
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# =======================================================================
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record = session.scalars(
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select(Cookie).where(Cookie.cookie_name == "chocolate chip")
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).first()
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print(record)
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record = session.scalars(
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select(Cookie).filter_by(cookie_name="chocolate chip")
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).first()
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print(record)
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stmt = select(Cookie).where(Cookie.cookie_name.like("chocolate chip"))
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print([c.cookie_name for c in session.scalars(stmt)])
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# =======================================================================
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# Вычисляемые колонки
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# =======================================================================
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stmt = select(Cookie.cookie_name, ("SKU-" + Cookie.cookie_sku).label("sku"))
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for r in session.execute(stmt):
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print(r)
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stmt = select(
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Cookie.cookie_name,
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func.cast(Cookie.quantity * Cookie.unit_cost, Numeric(12, 2)).label("inv_cost"),
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)
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print([(r.cookie_name, repr(r.inv_cost)) for r in session.execute(stmt)])
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stmt = select(Cookie).where(
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Cookie.quantity > 23, Cookie.unit_cost < Decimal("0.40")
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)
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print([(c.cookie_name,) for c in session.scalars(stmt)])
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stmt = select(Cookie).where(
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or_(
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Cookie.quantity.between(10, 50),
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Cookie.cookie_name.contains("chip"),
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)
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)
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print([(c.cookie_name,) for c in session.scalars(stmt)])
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# =======================================================================
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# UPDATE (ORM-объект)
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# =======================================================================
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cc_cookie = session.scalars(
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select(Cookie).filter_by(cookie_name="chocolate chip")
|
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).first()
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assert cc_cookie is not None
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cc_cookie.quantity = (cc_cookie.quantity or 0) + 120
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session.commit()
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print("cc_cookie.quantity =", cc_cookie.quantity)
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# UPDATE (bulk)
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session.execute(
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update(Cookie)
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.where(Cookie.cookie_name == "chocolate chip")
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.values(quantity=Cookie.quantity - 20)
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)
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session.commit()
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print(
|
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"after bulk update:",
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session.scalars(
|
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select(Cookie.quantity).where(Cookie.cookie_name == "chocolate chip")
|
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).one(),
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)
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# =======================================================================
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# DELETE (ORM)
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# =======================================================================
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dcc_cookie = session.scalars(
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select(Cookie).filter_by(cookie_name="dark chocolate chip")
|
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).one()
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session.delete(dcc_cookie)
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session.commit()
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assert (
|
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session.scalars(
|
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select(Cookie).filter_by(cookie_name="dark chocolate chip")
|
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).first()
|
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is None
|
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)
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|
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# DELETE (bulk)
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session.execute(delete(Cookie).where(Cookie.cookie_name == "molasses"))
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session.commit()
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assert (
|
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session.scalars(select(Cookie).filter_by(cookie_name="molasses")).first()
|
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is None
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)
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# =======================================================================
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# Пользователи и связи
|
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# =======================================================================
|
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cookiemon = User(
|
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username="cookiemon",
|
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email_address="mon@cookie.com",
|
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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
|
||||
|
||||
Reference in New Issue
Block a user