รบกวนช่วยดูโค๊ด Register form ทีคะ ติดปัญหาตรงที่่ตรวจ id และ username ซ้ำคะ

<?
include_once("connect.php");
$strsql="select * from employee where emp_id ='".trim($_POST['emp_id'])."'";
$strobj=mysql_query($strsql);
$rs=mysql_fetch_assoc($strobj);

if($rs)
{
	echo "Emp_ID Existed";
	echo "<br> Go to <a href='frm_register.php'>Register page</a>";
}

$strsql="select * from employee where username ='".trim($_POST['username'])."'";
$strobj=mysql_query($strsql);
$rs=mysql_fetch_assoc($strobj);

if($rs)
{
	echo "Username Existed";
	echo "<br> Go to <a href='frm_register.php'>Register page</a>";
}
else{
	$strsql="insert into employee (emp_id,username,password,emp_name,emp_lname,emp_position,emp_email,emp_status) values ('".$_POST['emp_id']."','".$_POST['username']."','".$_POST['password']."','".$_POST['emp_name']."','".$_POST['emp_lname']."','".$_POST['emp_position']."','".$_POST['emp_email']."','".$_POST['emp_status']."')";
	
	$rs=mysql_query($strsql);
	
	echo "Register Completed<br>";
	echo "<br> Go to <a href='frm_login.php'>Login page</a>";
	
}
mysql_close();
	
?>