怎样从mysql中随机获得一组数显示在php上

<?php
$arr_rand = array();//随机取数

$conn = mysql_connect("localhost", "mysql_user", "mysql_password");

if (!$conn) {
echo "Unable to connect to DB: " . mysql_error();
exit;
}

if (!mysql_select_db("mydbname")) {
echo "Unable to select mydbname: " . mysql_error();
exit;
}

$sql = "SELECT id as userid, fullname, userstatus
FROM sometable

$result = mysql_query($sql);

if (!$result) {
echo "Could not successfully run query ($sql) from DB: " . mysql_error();
exit;
}

if (mysql_num_rows($result) == 0) {
echo "No rows found, nothing to print so am exiting";
exit;
}

// While a row of data exists, put that row in $row