Question

Quite a complex question:

At the moment I have a table called “timetable”. This is updated when someone books a slot (this is for a radio booking system). What I would like is a PHP file that I can have run every 15 minutes as a cron job. In PHP script what I’d like it to do is count how many slots a radio presenter has booked via the “username” field in the “timetable” table. Then I would like it to update a field in another table called “users” in a field called “slot_count” with the amount of slots which were found in the “timetable” table under their “username”.

At the moment I have a script which pulls all the booked slots with their presenter “username”‘s into a table:

<?php 
include("../config.php");
include("functions.php");
if($logged["level"] == "HDJ" OR $logged["level"] == "SA") {

echo "<table width=\"580px\" class=\"board\" border=\>";

$order = "SELECT * FROM timetable WHERE username <> 'No DJ'";
$result = mysql_query($order);

// Error checking
if (!$result) {
  // output error, take other action
}
else {
  while ($row=mysql_fetch_array($result)){
     // Append all results onto an array
     $rowset[] = $row;
  }
}
    foreach ($rowset as $row) {
  echo "<tr><td>" . htmlspecialchars($row['username']) . "</td></tr>";
}

    } else {
echo ("<div class=\"caution\">Access is denied.</div>");
}
?> 

Any ideas?

Answer 1

Storing this redundant data in your users table is unnecessary. As long as the tables are indexed appropriately the join and count are trivial –

SELECT users.*, COUNT(timetable.username) AS num_slots
FROM users
LEFT JOIN timetable
    ON users.username = timetable.username
GROUP BY users.id