sum and count with joined tables - mysql

Question

Haven't come across a situation like this so not sure how to correct it. I'm guessing a sub query is needed?
I need the SUM of votes.vote and the COUNT of votes.vote. This allows me to calculate a rating (sum of all votes / # of votes = rating) for the location selected.
Here is the query with * and static binding to make it easier to understand :
//prepare
$stmt = $db->prepare("
SELECT SQL_CALC_FOUND_ROWS
*,
COALESCE(SUM(votes.vote),0) AS vote_total,
COUNT(votes.vote) AS number_votes
FROM locations
LEFT JOIN tables
ON tables.location_id = locations.location_id
LEFT JOIN votes
ON votes.location_id = locations.location_id
LEFT JOIN events
ON events.location_id = locations.location_id
WHERE locations.location_id = :location_id
LIMIT :limit OFFSET :offset
");
//bindings
$binding = array(
'location_id' => 11,
'limit' => 20,
'offset' => 0
);
//execute
$stmt->execute($binding);
//results
$results = $stmt->fetchAll(PDO::FETCH_ASSOC);
There are 11 events joined to this location. There are only two votes joined to it (a value of 3 and a value of 4). I am getting the following :
[vote_total] => 77 (should be 7, but is 7*11)
[number_votes] => 22 (should be 2, but is 2*11)
Aside from that only one result is returned rather than 11. If I remove the votes table join and the SUM/COUNT selects for it all 11 results are shown as they should be.
Is it possible to get the SUM and COUNT totals for votes.vote in the same query in some way or will a separate query be needed just to get those values?

Answer 1

My best guess based on your description of the problem is that you want one row per event. If so:
SELECT SQL_CALC_FOUND_ROWS e.*
COALESCE(SUM(v.vote), 0) AS vote_total,
COUNT(v.vote) AS number_votes
FROM locations l LEFT JOIN
tables
ON t.location_id = l.location_id LEFT JOIN
votes v
ON v.location_id = l.location_id LEFT JOIN
events e
ON e.location_id = l.location_id
WHERE l.location_id = :location_id
GROUP BY e.event_id
LIMIT :limit OFFSET :offset;