Counting records in MySQL with a complicated HAVING Statement - mysql

Question

I have a query which returns map markers within a radius (in miles) of a given position (lat/lng). My query works when reading the data, but I am wanting to set up pagination so need to count the records first to determine how many pages of data I will have.
My query is :
SET #LAT := 53.068464;
SET #LNG := -4.076113;
SET #Miles := 10;
SELECT (3959 * acos( cos( radians(#LAT) ) * cos( radians( M.Lat ) ) * cos(
radians( M.Lng ) - radians(#LNG) ) + sin( radians(#LAT) ) * sin( radians(
M.Lat ) ) ) ) AS distance, M.MarkerId, M.Title
FROM Markers AS M
HAVING distance < #Miles
ORDER BY M.DateStamp desc, Distance
I have tried
SELECT COUNT(MarkerId)
FROM Markers
HAVING (3959 * acos( cos( radians(#LAT) ) * cos( radians( Lat ) ) * cos(
radians( Lng ) - radians(#LNG) ) + sin( radians(#LAT) ) * sin( radians( Lat )
) ) ) < #Miles
but it fails trying to reference the Lat and Lng fields from the Markers table.

Answer 1

There are two methods. One is to use a subquery:
SELECT COUNT(*)
FROM (SELECT (3959 * acos( cos( radians(#LAT) ) * cos( radians( M.Lat ) ) * cos(
radians( M.Lng ) - radians(#LNG) ) + sin( radians(#LAT) ) * sin( radians(
M.Lat ) ) ) ) AS distance, M.MarkerId, M.Title
FROM Markers AS M
HAVING distance < #Miles
) x
The second method is to use SQL_CALC_FOUND_ROWS and then the FOUND_ROWS() function:
SELECT SQL_CALC_FOUND_ROWS (3959 * acos( cos( radians(#LAT) ) * cos( radians( M.Lat ) ) * cos(
radians( M.Lng ) - radians(#LNG) ) + sin( radians(#LAT) ) * sin( radians(
M.Lat ) ) ) ) AS distance, M.MarkerId, M.Title
FROM Markers AS M
HAVING distance < #Miles
ORDER BY M.DateStamp desc, Distance ;
SELECT FOUND_ROWS();

Answer 2

$str1="select SQL_CALC_FOUND_ROWS (3959 * acos( cos( radians(#LAT) ) * cos( radians( M.Lat ) ) * cos(
radians( M.Lng ) - radians(#LNG) ) + sin( radians(#LAT) ) * sin( radians(
M.Lat ) ) ) ) AS distance, M.MarkerId, M.Title
FROM Markers AS M
HAVING distance < #Miles
ORDER BY M.DateStamp desc, Distance limit ".$offset.",".$limit;
$q1 = mysql_query($str1);
$result=array();
$str2="SELECT FOUND_ROWS() AS Count";
$q2 = mysql_query($str2);
while($objCount= $q2->fetch_assoc()) {
$result["TotalRows"] = $objCount['Count'];
}
if ($q1->num_rows > 0) {
$result["Rows"] = mysql_result($q1);
} else {
$result["Rows"] = array();
}
return $result;