PHP +mysql authentication code

<?php 
$uname=$_POST["username"]; 
$pwd=$_POST["password"]; 
$link = mysql_connect('localhost', 'root', '123456') 
or die('Could not connect: ' . mysql_error()); 
mysql_select_db('ruida') or die('Could not select database'); 
//Executing SQL queries
$query = 'SELECT * FROM user'; 
$result = mysql_query($query) or die('Query failed: ' . mysql_error()); 
while($row=mysql_fetch_array($result)){ 
if($uname==$row['username'] && $pwd==$row['password']) 
{ 
//Page jump
} 
else 
echo 'error!';} 
//Release result set
mysql_free_result($result); 
//Close the connection
mysql_close($link); 
?>