How to search for events in 5 km radius - mysql

Question

I'm trying to select events in a 5 km radius and order them by likes and from oldest to newest. I know how to select events and order them by likes, but I can't figure this one out. The problem maybe is that the location is stored in a different table.
Database structure:
event plusone (like) location
id_event id_plusone id_location
location_id event_id lat
... user_id lon
... city_id
full_name
....
The SQL statement I'm trying:
SELECT 3956 * 2 * ASIN(
SQRT(POWER(SIN((50.127946 - abs(l.lat)) * pi()/180 / 2),2) + COS(50.127946 * pi()/180 ) *
COS(abs(l.lat) * pi()/180) * POWER(SIN((14.4882912 - l.lon) * pi()/180 / 2), 2) )) AS distance,e.*,COUNT( p.id_plusone ) AS
likes
FROM
event e,location l
LEFT JOIN plusone p ON p.event_id = e.id_event
WHERE
e.location_id = l.id_location AND distance<=5 GROUP BY e.id_event
ORDER BY e.timestamp DESC,likes DESC
The huge column at the beginning is calculation of distance of the event from user position using latitude and longitude.
This is what I get from the SQL debugger:
#1054 - Unknown column 'distance' in 'where clause'
Does anybody know how to do this?

Answer 1

Is hard to track where the error is, you should try to solve the distance part first.
SELECT
event_id,
3956 * 2 * ASIN(SQRT( POWER(SIN((50.127946 - abs(l.lat)) * pi()/180 / 2),2)
+ COS(50.127946 * pi()/180 ) * COS(abs(l.lat) * pi()/180) * POWER(SIN((14.4882912 – l.lon) * pi()/180 / 2), 2) )) AS distance,
FROM event e
JOIN location l
WHERE distance <= 5
And then join to back to the event table
SELECT e.*, count(p.id_plusone)
FROM event e
LEFT JOIN plusone p
ON p.event_id = e.id_event
JOIN ( Previous Distance Query) d
ON e.event_id = d.event_id
GROUP BY e.id_event
ORDER BY e.timestamp DESC, likes DESC
and btw, this group_by will bring you event_id plus random values for e.* so be carefull

Answer 2

$latitudeD= latitude;
$longitudeD = longitude;
SELECT event,
SQRT(
POW(69.1 * (coordX - $latitudeD), 2) +
POW(69.1 * ($longitudeD - coordY) * COS(coordX / 57.3), 2)) AS distance
FROM db.table WHERE SQRT(
POW(69.1 * (coordX - $latitudeD), 2) +
POW(69.1 * ($longitudeD - coordY) * COS(coordX / 57.3), 2)) < 50 ORDER BY distance
;