第四章：数据库

1. sqlite3 标准库

标准库内置 SQLite 驱动，适合原型与嵌入式场景。生产可换 PostgreSQL/MySQL 驱动（如 psycopg、mysqlclient），连接 URL 与事务概念相通。

import sqlite3

conn = sqlite3.connect("app.db")
conn.execute(
    "CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY, name TEXT NOT NULL)"
)
conn.commit()

2. 参数化查询（防注入）

# 使用占位符，勿拼接字符串
conn.execute("INSERT INTO users (name) VALUES (?)", ("alice",))
conn.execute("SELECT id, name FROM users WHERE name = ?", ("alice",))

3. 事务

try:
    conn.execute("UPDATE accounts SET balance = balance - 10 WHERE id = 1")
    conn.execute("UPDATE accounts SET balance = balance + 10 WHERE id = 2")
    conn.commit()
except Exception:
    conn.rollback()
    raise