在网络安全领域，SQL注入是一种常见的攻击手段，它允许攻击者通过在数据库查询中插入恶意SQL代码来操纵数据库。虽然通常情况下，SQL注入攻击会利用引号来绕过输入验证，但也有一些技巧可以不包含引号进行攻击。本文将揭秘这些不包含引号的SQL注入技巧，并探讨如何防范此类攻击。
一、不包含引号的SQL注入技巧
- 注释绕过：
攻击者可以通过在SQL查询中插入注释来绕过引号。例如：
SELECT * FROM users WHERE username = 'admin' -- AND password = '123456'
在这里，-- 是SQL中的注释符号，它将后面的语句视为注释，从而绕过了密码验证。
- 联合查询：
攻击者可以通过联合查询来获取不需要的列。例如：
”`sql SELECT * FROM users WHERE username = ‘admin’ 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, 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