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MySQL 面试真题（带答案）

news 来源：原创 2024/9/20 6:06:45

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：

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.connectordef 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.lastrowidfor 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.priceFROM orders oJOIN order_items i ON o.order_id = i.order_idWHERE 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.')