Select

$select = "select FLOOR(RAND() * COUNT(*)) AS `random_var` from admin_reviews";	
$res = mysql_query($select);
$row = mysql_fetch_assoc($res);	
$random_var = $row['random_var'];	

				
$select = "select * FROM `admin_reviews` LIMIT " . $random_var . ", 1";
$res = mysql_query($select);
while($row = mysql_fetch_assoc($res))
{
...

SELECT id, LENGTH(`Company`) cnt, `Company` FROM `users_change_data` WHERE 1 order by cnt desc limit 1

//Простой запрос
$query = "Select id From reg where name_1 = '$name_1' and name_2 = '$name_2' and name_3 = '$name_3' and email = '$email'  limit 1";	
$res = mysql_query($query);
$id =   mysql_result($res, 0, 0);


//По именам
$query_d_m = "select * from reg where id > 0";
$res = mysql_query($query_d_m);
$row = mysql_fetch_assoc($res);	
$id= $row['id'];
$name= $row['name'];

или

		$row_vk = mysql_fetch_array(mysql_query("SELECT vkontakte FROM djs WHERE id='" . mysql_real_escape_string($id) . "'"));
		
		if($row_vk['vkontakte'] != '')
		{
			echo 'ok' . $row_vk['vkontakte'];
			
		}	


//В массив
$arr = array();
$query_d_c = "select * from bar order by type";			
$res = mysql_query($query_d_c);
while ($row = mysql_fetch_assoc($res)) {
	$arr[] = $row;
}	
$count_arr = count($arr);