那么，如果我的用户名是：
1' or '1'='1那么，你的查询语句将会变成：
select * from admin where username='1 or '1'='1' and password='"&pwd&"'"这样你的查询语句就通过了，从而就可以进入你的管理界面。
所以防范的时候需要对用户的输入进行检查。特别是一些特殊字符，比如单引号，双引号，分号，逗号，冒号，连接号等进行转换或者过滤。
需要过滤的特殊字符及字符串有：
net userxp_cmdshell/addexec master.dbo.xp_cmdshellnet localgroup administratorsselectcountAsccharmid':"insertdelete fromdrop tableupdatetruncatefrom%
下面是我写的两种关于解决注入式攻击的防范代码，供大家学习参考！
js版的防范SQL注入式攻击代码～：
[CODE START]<script language="javascript"><!--var url = location.search;var re=/^\?(.*)(select%20|insert%20|delete%20from%20|count\(|drop%20table|update%20truncate%20|asc\(|mid\(|char\(|xp_cmdshell|exec%20master|net%20localgroup%20administrators|\"|:|net%20user|\'|%20or%20)(.*)$/gi;var e = re.test(url);if(e) {alert("地址中含有非法字符～");location.href="error.asp";}//--><script>[CODE END]
asp版的防范SQL注入式攻击代码～：
[CODE START]＜%On Error Resume NextDim strTempIf LCase(Request.ServerVariables("HTTPS")) = "off" ThenstrTemp = "http://"ElsestrTemp = "https://"End IfstrTemp = strTemp & Request.ServerVariables("SERVER_NAME")If Request.ServerVariables("SERVER_PORT") <> 80 Then strTemp = strTemp & ":" & Request.ServerVariables("SERVER_PORT")strTemp = strTemp & Request.ServerVariables("URL")If Trim(Request.QueryString) <> "" Then strTemp = strTemp & "?" & Trim(Request.QueryString)strTemp = LCase(strTemp)If Instr(strTemp,"select%20") or Instr(strTemp,"insert%20") or Instr(strTemp,"delete%20from") or Instr(strTemp,"count(") or Instr(strTemp,"drop%20table") or Instr(strTemp,"update%20") or Instr(strTemp,"truncate%20") or Instr(strTemp,"asc(") or Instr(strTemp,"mid(") or Instr(strTemp,"char(") or Instr(strTemp,"xp_cmdshell") or Instr(strTemp,"exec%20master") or Instr(strTemp,"net%20localgroup%20administrators") or Instr(strTemp,":") or Instr(strTemp,"net%20user") or Instr(strTemp,"'") or Instr(strTemp,"%20or%20") thenResponse.Write "＜script language='javascript'＞"Response.Write "alert('非法地址！！');"Response.Write "location.href='error.asp';"Response.Write "＜script＞"End If%＞[CODE END]