引言
SQL注入是一种常见的网络安全威胁，它允许攻击者通过在输入数据中插入恶意SQL代码，从而攻击数据库。本文将详细介绍SQL注入的原理、常见攻击语句以及防范攻略。
SQL注入原理
SQL注入攻击利用了应用程序对用户输入数据的信任。当应用程序将用户输入的数据直接拼接到SQL语句中时，攻击者可以插入恶意SQL代码，进而控制数据库。
常见攻击语句
以下是一些常见的SQL注入攻击语句：
- 联合查询（Union Query）：
' OR '1'='1
该语句通过插入 ' OR '1'='1，使得整个查询条件始终为真，从而绕过正常的数据验证。
- 信息泄露（Information Disclosure）：
”`sql ‘ 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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