从表中选择有误

Question

$mainuser=$_POST['mainuser'];


$likeduser=$_POST['likeduser'];

$workcode=$_POST['workcode'];


$sqlQ="select * from shablike where 'mainuser'='$mainuser' and  'workcode'='$workcode'  ";
$result=mysql_Query($sqlQ);


if($result){
print "again";

  }

else {
$sqlQ1="insert into shablike (workcode,mainuser,likeduser)     VALUES('$workcode','$mainuser','$likeduser')";
$result1=mysql_Query($sqlQ1);
if($result1)
{print "ok";}

 }

mysql_close($con);

＆GT;

这是我的简单代码 但它dosnt work.i想要选择mainuser = $ mainuser和workcode = $ workcode

的行

请帮助我 谢谢所有