PHP MySQL Where clause learning

$con = mysql_connect("localhost","peter","abc123");
if (!$con)
  {
  die('Could not connect: ' . mysql_error());
  }
mysql_select_db("my_db", $con);
$result = mysql_query("SELECT * FROM Persons
WHERE FirstName='Peter'");
while($row = mysql_fetch_array($result))
  {
  echo $row['FirstName'] . " " . $row['LastName'];
  echo "";
  }
?>

输出： Peter Griffin