Averaging a number over multiple rows, selected by day - php

Question

I'm writing up a statistics script for a service I run. I want to work out the average number of rows per day on a last 3 days, weekly, monthly and yearly basis. My basic thought is something like this to grab the average:
<?php
function getDayNumber($day)
{
$start = strtotime("last monday");
$q = mysql_query(sprintf("SELECT COUNT(*) as count FROM mytable WHERE dayname(datetime) = "%s" AND unix_timestamp(datetime) > %s",$day,$start));
$row = mysql_fetch_assoc($q);
return $row['count'];
}
$monday = getDayNumber("Monday");
$tuesday = getDayNumber("Tuesday");
$wednesday = getDayNumber("Wednesday");
$thursday = getDayNumber("Thursday");
$friday = getDayNumber("Friday");
$average = ($monday+$tuesday+$wednesday+$thursday+$friday)/5;
?>
The above is just psuedo code written from my head. I can't think of a better method though.
Is this possible to do via nested/joined queries? I'll need to be able to do it on a daily, weekly, monthly... etc basis. I figure if I can find a way to pull all the data in MySQL, I can just add all the count(*)'s together and divide them via the number of responses.
Is this feasible?
Any help is appreciated - thanks all!

Answer 1

I suggest finding the date range for each data set then running your query. Hope this helps.
<?php
/**
* Get the average number of rows that were created
* during the given date range.
*
* #param string $range The date range to look for
* #return integer The average number of rows created in the given range
*/
function getAverageRows($range)
{
$date_begin = null;
$date_end = null;
switch($range)
{
case 'year':
// Calculate the beginning and end datetime of the past year
$date_begin = FIRST_DAY_OF_YEAR . ' 00:00:00';
$date_end = LAST_DAY_OF_YEAR . ' 23:59:59';
break;
case 'month':
// Calculate the beginning and end datetime of the past month
$date_begin = FIRST_DAY_OF_MONTH . ' 00:00:00';
$date_end = LAST_DAY_OF_MONTH . ' 23:59:59';
break;
case 'week':
// Calculate the beginning and end datetime of the past week
$date_begin = FIRST_DAY_OF_WEEK . ' 00:00:00';
$date_end = LAST_DAY_OF_WEEK . ' 23:59:59';
break;
default:
// Calculate the beginning and end datetime of the past three days
$date_begin = SEVENTY_SIX_HOURS_AGO;
$date_end = now();
break;
}
$query = "SELECT COUNT(*) FROM mytable WHERE datetime >= '{$date_begin}' AND datetime <= '{$date_end}'";
// Get and return query results
}
echo "Average Rows:<br/>";
echo "Past three days: " . getAverageRows() . "<br/>";
echo "Past week: " . getAverageRows('week') . "<br/>";
echo "Past Month: " . getAverageRows('month') . "<br/>";
echo "Past Year: " . getAverageRows('year') . "<br/>";