MySQL 面试真题（带答案）

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MySQL 场景面试题

场景1：用户注册和登录系统

1.1 数据库设计

设计一个简单的用户注册和登录系统，包含用户表 users，表结构如下：

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CREATE TABLE users (
    user_id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL UNIQUE,
    password VARCHAR(255) NOT NULL,
    email VARCHAR(100) NOT NULL UNIQUE,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

1.2 用户注册

用户注册时，需要将用户名、密码和邮箱存入数据库。使用如下 SQL 语句进行用户注册：

INSERT INTO users (username, password, email) 
VALUES ('test_user', 'password123', 'test_user@example.com');

假设在代码中，使用准备好的语句进行注册操作：

import mysql.connector
def register_user(username, password, email):
    conn = mysql.connector.connect(user='root', password='password', host='127.0.0.1', database='test_db')
    cursor = conn.cursor()
    
    try:
        cursor.execute("INSERT INTO users (username, password, email) VALUES (%s, %s, %s)", (username, password, email))
        conn.commit()
        print("User registered successfully")
    except mysql.connector.Error as err:
        print("Error: {}".format(err))
    finally:
        cursor.close()
        conn.close()
# Example usage
register_user('test_user', 'password123', 'test_user@example.com')

1.3 用户登录

用户登录时，需要验证用户名和密码。使用如下 SQL 语句进行验证：

SELECT * FROM users WHERE username = 'test_user' AND password = 'password123';

假设在代码中，使用准备好的语句进行登录验证：

def login_user(username, password):
    conn = mysql.connector.connect(user='root', password='password', host='127.0.0.1', database='test_db')
    cursor = conn.cursor()
    
    cursor.execute("SELECT * FROM users WHERE username = %s AND password = %s", (username, password))
    user = cursor.fetchone()
    
    if user:
        print("Login successful")
    else:
        print("Invalid username or password")
    
    cursor.close()
    conn.close()
# Example usage
login_user('test_user', 'password123')

场景2：订单管理系统

2.1 数据库设计

设计一个简单的订单管理系统，包括订单表 orders 和订单详情表 order_items，表结构如下：

CREATE TABLE orders (
    order_id INT AUTO_INCREMENT PRIMARY KEY,
    user_id INT NOT NULL,
    order_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    total_amount DECIMAL(10, 2) NOT NULL
);
CREATE TABLE order_items (
    item_id INT AUTO_INCREMENT PRIMARY KEY,
    order_id INT NOT NULL,
    product_id INT NOT NULL,
    quantity INT NOT NULL,
    price DECIMAL(10, 2) NOT NULL,
    FOREIGN KEY (order_id) REFERENCES orders(order_id)
);

2.2 创建订单

创建订单时，需要在 orders 表中插入订单记录，并在 order_items 表中插入订单项记录。使用如下 SQL 语句进行插入：

INSERT INTO orders (user_id, total_amount) VALUES (1, 100.00);
INSERT INTO order_items (order_id, product_id, quantity, price) VALUES (LAST_INSERT_ID(), 101, 2, 50.00);

假设在代码中，使用事务进行创建订单操作：

def create_order(user_id, order_items):
    conn = mysql.connector.connect(user='root', password='password', host='127.0.0.1', database='test_db')
    cursor = conn.cursor()
    
    try:
        cursor.execute("INSERT INTO orders (user_id, total_amount) VALUES (%s, %s)", (user_id, sum(item['quantity'] * item['price'] for item in order_items)))
        order_id = cursor.lastrowid
        
        for item in order_items:
            cursor.execute("INSERT INTO order_items (order_id, product_id, quantity, price) VALUES (%s, %s, %s, %s)", (order_id, item['product_id'], item['quantity'], item['price']))
        
        conn.commit()
        print("Order created successfully")
    except mysql.connector.Error as err:
        conn.rollback()
        print("Error: {}".format(err))
    finally:
        cursor.close()
        conn.close()
# Example usage
order_items = [
    {'product_id': 101, 'quantity': 2, 'price': 50.00},
    {'product_id': 102, 'quantity': 1, 'price': 100.00}
]
create_order(1, order_items)

2.3 查询订单

查询订单时，需要关联 orders 表和 order_items 表。使用如下 SQL 语句进行查询：

SELECT o.order_id, o.order_date, o.total_amount, i.product_id, i.quantity, i.price
FROM orders o
JOIN order_items i ON o.order_id = i.order_id
WHERE o.user_id = 1;

假设在代码中，进行查询订单操作：

def get_orders(user_id):
    conn = mysql.connector.connect(user='root', password='password', host='127.0.0.1', database='test_db')
    cursor = conn.cursor()
    
    cursor.execute("""
        SELECT o.order_id, o.order_date, o.total_amount, i.product_id, i.quantity, i.price
        FROM orders o
        JOIN order_items i ON o.order_id = i.order_id
        WHERE o.user_id = %s
    """, (user_id,))
    
    orders = cursor.fetchall()
    
    for order in orders:
        print(order)
    
    cursor.close()
    conn.close()
# Example usage
get_orders(1)

场景3：博客系统

3.1 数据库设计

设计一个简单的博客系统，包括文章表 posts 和评论表 comments，表结构如下：

CREATE TABLE posts (
    post_id INT AUTO_INCREMENT PRIMARY KEY,
    title VARCHAR(255) NOT NULL,
    content TEXT NOT NULL,
    author_id INT NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);
CREATE TABLE comments (
    comment_id INT AUTO_INCREMENT PRIMARY KEY,
    post_id INT NOT NULL,
    user_id INT NOT NULL,
    comment TEXT NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    FOREIGN KEY (post_id) REFERENCES posts(post_id)
);

3.2 发布文章

发布文章时，需要在 posts 表中插入记录。使用如下 SQL 语句进行插入：

INSERT INTO posts (title, content, author_id) VALUES ('My First Post', 'This is the content of my first post.', 1);

假设在代码中，进行发布文章操作：

def create_post(title, content, author_id):
    conn = mysql.connector.connect(user='root', password='password', host='127.0.0.1', database='test_db')
    cursor = conn.cursor()
    
    try:
        cursor.execute("INSERT INTO posts (title, content, author_id) VALUES (%s, %s, %s)", (title, content, author_id))
        conn.commit()
        print("Post created successfully")
    except mysql.connector.Error as err:
        print("Error: {}".format(err))
    finally:
        cursor.close()
        conn.close()
# Example usage
create_post('My First Post', 'This is the content of my first post.', 1)

3.3 评论功能

用户可以对文章进行评论，需要在 comments 表中插入记录。使用如下 SQL 语句进行插入：

INSERT INTO comments (post_id, user_id, comment) VALUES (1, 2, 'This is a comment.');

假设在代码中，进行评论操作：

def add_comment(post_id, user_id, comment):
    conn = mysql.connector.connect(user='root', password='password', host='127.0.0.1', database='test_db')
    cursor = conn.cursor()
    
    try:
        cursor.execute("INSERT INTO comments (post_id, user_id, comment) VALUES (%s, %s, %s)", (post_id, user_id, comment))
        conn.commit()
        print("Comment added successfully")
   
 except mysql.connector.Error as err:
        print("Error: {}".format(err))
    finally:
        cursor.close()
        conn.close()
# Example usage
add_comment(1, 2, 'This is a comment.')

以上是关于 MySQL 的详细场景面试题及解答，涵盖了用户注册和登录系统、订单管理系统和博客系统的具体场景和代码实现，供参考学习。

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