Retrieving mysql statistical data using PHP regular intervals and including null data - php

Question

So I am trying to build out some nice stats displays for my app. I can do this because I keep hit stats in a table. It simply tracks the hits plus some other nice data and the time it occurs. I can query the db to show me how many hits occurred on a particular day or on each day for the past x days as in the code below. However the code below only returns dates for which there is data. I would like to show the last 30 days of hits regardless of whether a day has a hit or not. Thoughts?
SELECT DATE(time) AS theday, COUNT( * ) AS thecount
FROM stats
WHERE time <= curdate( )
AND time >= DATE_SUB( curdate(), INTERVAL 30 DAY )
GROUP BY theday ORDER BY time DESC
Produces
theday thecount
2011-11-22 5
2011-11-21 9
2011-11-18 10
2011-11-16 1
2011-11-11 2
2011-11-10 15
2011-11-09 2
2011-10-26 1
2011-10-24 6
As you can see it skips dates with no results. I understand why this is, as there are no rows with those dates in the db. I am wondering how I would produce a query that works almost like the above but has all the dates for said interval. IE: the last 30 days.

Answer 1

You have 3 options:
try to iterate the dates in the application logic (php)
generate a (temporary) table filled with the dates you need and left join with it
use mysql stored procedure solution like in this answer
Example for app logic implementation:
<?php
date_default_timezone_set('Europe/Paris');
$startdate = strtotime('2011-11-01 00:00:01');
$days = 60;
$found_data = array( // this is generated by 1 mysql query
array('date_field' => '2011-11-02', 'count' => 5),
array('date_field' => '2011-11-03', 'count' => 1),
array('date_field' => '2011-11-04', 'count' => 6),
array('date_field' => '2011-11-08', 'count' => 9),
array('date_field' => '2011-11-09', 'count' => 3),
array('date_field' => '2011-11-10', 'count' => 5),
array('date_field' => '2011-11-12', 'count' => 1),
array('date_field' => '2011-11-15', 'count' => 1),
array('date_field' => '2011-11-18', 'count' => 4),
array('date_field' => '2011-11-21', 'count' => 9),
array('date_field' => '2011-11-23', 'count' => 1),
array('date_field' => '2011-11-28', 'count' => 8),
array('date_field' => '2011-11-30', 'count' => 6),
);
foreach ($found_data as $counts) { // we convert the results to a usable form, you can do this in the query, too
$count_info[$counts['date_field']] = $counts['count'];
}
for ($i = 0; $i <= $days; $i++) {
$date = date('Y-m-d', $startdate+$i*60*60*24);
printf("%s\t%s\n", $date, array_key_exists($date, $count_info) ? $count_info[$date] : 0);
}
?>