What are the methods to prevent sql injection?

What are the methods to prevent SQL injection, specific code examples are required

SQL injection is a common network security threat, which allows attackers to construct Malicious input to modify, delete or leak data in the database. In order to effectively prevent SQL injection attacks, developers need to take a series of security measures. This article will introduce several commonly used methods to prevent SQL injection and give corresponding code examples.

Method 1: Use parameterized query
Parameterized query is a way to use placeholders to replace actual parameter values, thereby reducing the possibility of SQL injection. The following is a Python sample code using parameterized queries:

import pymysql

# 建立数据库连接
conn = pymysql.connect(host='localhost', user='root', password='123456', db='mydb')

# 创建游标对象
cursor = conn.cursor()

# 执行参数化查询
username = input("请输入用户名：")
password = input("请输入密码：")
sql = "SELECT * FROM user WHERE username = %s AND password = %s"
cursor.execute(sql, (username, password))

# 获取查询结果
result = cursor.fetchall()

# 处理查询结果
if result:
    print("登录成功！")
else:
    print("用户名或密码错误！")

# 关闭游标和数据库连接
cursor.close()
conn.close()

Method 2: Using the ORM framework
The ORM (Object Relational Mapping) framework can convert database table operations into object-oriented method calls, effectively This effectively avoids the problem of SQL injection.

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

# 建立数据库连接
engine = create_engine('mysql+pymysql://root:123456@localhost/mydb')
Session = sessionmaker(bind=engine)
session = Session()

# 执行查询
username = input("请输入用户名：")
password = input("请输入密码：")
result = session.query(User).filter_by(username=username, password=password).first()

# 处理查询结果
if result:
    print("登录成功！")
else:
    print("用户名或密码错误！")

# 关闭数据库连接
session.close()

Method 3: Input verification and filtering
Validating and filtering the validity of user-entered data is an important step to prevent SQL injection. The following is a simple PHP sample code:

<?php
$username = $_POST['username'];
$password = $_POST['password'];

// 验证输入的数据
if (!preg_match("/^[a-zA-Z0-9]{6,}$/", $username)) {
    die("用户名不合法！");
}

// 过滤特殊字符
$username = addslashes($username);
$password = addslashes($password);

// 执行查询
$sql = "SELECT * FROM user WHERE username = '$username' AND password = '$password'";
$result = mysqli_query($conn, $sql);

// 处理查询结果
if (mysqli_num_rows($result) > 0) {
    echo "登录成功！";
} else {
    echo "用户名或密码错误！";
}

// 关闭数据库连接
mysqli_close($conn);
?>

In the above code, we use regular expressions to validate the entered user name, only letters and numbers are allowed, and the length must not be less than 6 characters. At the same time, the input data is filtered by using the addslashes function and special characters are escaped, thereby avoiding the possibility of SQL injection.

To sum up, in order to prevent SQL injection attacks, developers can adopt parameterized queries, use ORM frameworks, and input validation and filtering. At the same time, reasonable permission control and regular update of system patches can also effectively improve system security.

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