Calculating average from a percent - php

Question

I am using DW to create record set that calculates the percentage from a table grouped by hospital name. I need to get the average of the percentage (by summation of the percentage divided by the number of hospital). I have only one table.
mysql_select_db($database_localapconnect, $localapconnect);
$query_Recordset1 = "SELECT COUNT(IF(ap_intervalname = 'Less than or equal to 12 hours', ap_intervalname, NULL))/ COUNT(ap_intervalname) *100 AS 'percent' FROM maintble GROUP BY `hospitalname`";
$Recordset1 = mysql_query($query_Recordset1, $localapconnect) or die(mysql_error());
$totalRows_Recordset1 = mysql_num_rows($Recordset1);
while($row_Recordset1 = mysql_fetch_array($Recordset1)) {
print_r( $row_Recordset1['percent'].'<br>');
}
print_r ($totalRows_Recordset1).'<br>' ;
echo sum($row_Recordset1['percent'])/$totalRows_Recordset1;
result:
83.0189
98.0000
86.2745
68.0365
94.9686
78.4314
6
I get the following error:
Fatal error: Call to undefined function sum() in C:\wamp\www\ap_database\Untitled-1.php on line 49

Answer 1

The function sum doesn't exist in PHP. If you want the sum of the elements of an array, you should use array_sum
But, in this specific case, I think it's better sum inside the loop, because you are already accessing all the elements anyway...
For example, like this:
$totalRows_Recordset1 = mysql_num_rows($Recordset1);
$sum = 0.0;
while($row_Recordset1 = mysql_fetch_array($Recordset1)) {
print_r( $row_Recordset1['percent'].'<br>');
$sum += $row_Recordset1['percent'];
}
print_r ($totalRows_Recordset1).'<br>' ;
echo $sum/$totalRows_Recordset1;

Answer 2

The easiest way is to use a subquery:
SELECT avg(percent)
FROM (SELECT AVG(CASE WHEN ap_intervalname = 'Less than or equal to 12 hours' THEN 100.0
ELSE 0 END) AS percent
FROM maintble
GROUP BY `hospitalname`
) m;

Answer 3

You're calling sum() in this line of php code.
sum($row_Recordset1['percent'])/$totalRows_Recordset1; /* mistake */
But that doesn't make sense. For one thing, $row_Recordset1['percent'] is just a plain old number. For another thing, php doesn't have a built in sum() function.
If you don't want to use SQL to do that computation, you need to add up the values in your recordset processing loop.
$sum = 0.0;
$count = 0;
while($row_Recordset1 = mysql_fetch_array($Recordset1)) {
$count ++;
$sum += $row_Recordset1['percent'];
print_r( $row_Recordset1['percent'].'<br>');
}
echo $sum / $count;
Notice I counted the rows explicitly rather than relying on num_rows(). That's for a good reason; under some circumstances num_rows() is not reliable before you read the recordset.