引言
SQL注入是一种常见的网络攻击手段，攻击者通过在输入字段中插入恶意SQL代码，从而获取、修改或删除数据库中的数据。本文将深入解析手工SQL注入的技巧，帮助读者了解并掌握数据库安全漏洞，提升网络安全防护能力。
一、SQL注入原理
SQL注入攻击主要利用了应用程序对用户输入数据的处理不当。以下是一个简单的SQL查询示例：
SELECT * FROM users WHERE username = 'admin' AND password = '123456';
当用户输入正确的用户名和密码时，查询将返回结果。然而，如果应用程序没有对用户输入进行适当的过滤和验证，攻击者就可以通过以下方式构造恶意SQL语句：
' OR '1'='1' --'
这条恶意SQL语句会绕过正常的用户名和密码验证，导致查询返回所有用户数据。
二、手工SQL注入技巧
1. 基本注入技巧
（1）数字型注入
通过在输入字段中插入数字，观察查询结果的变化，从而获取数据库结构信息。
”`sql 1’ UNION SELECT null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, null, 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