仅获取使用 PHP 显示的 mysql 表的一行

我目前有这段代码，可以显示 mysql 表中的所有条目行并将它们显示在网页上;

<?php
$servername = "localhost";
$username = "appuser1";
$password = "*****";
$dbname = "acmefg_app";
$row = mysql_fetch_array(mysql_query("SELECT jobnumber FROM appdata WHERE id = '5608' LIMIT 1"));
// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
     die("Connection failed: " . $conn->connect_error);
} 
$sql = "SELECT id, jobnumber, assetnumber FROM appdata";
$result = $conn->query($sql);
if ($result->num_rows > 0) {
     // output data of each row
     while($row = $result->fetch_assoc()) {
         echo "<br> id: ". $row["id"].  "<br>";
         echo "<br> Job number: ". $row["jobnumber"]. "<br>";
         echo "<br> Asset number: " . $row["assetnumber"] . "<br>";
     }
} else {
     echo "0 results";
}
$conn->close();
?>  

如何更改此设置，使其仅显示一个结果？假设在这种情况下，我想显示 id 为 5611 的行？非常感谢