Question

RIGHT JOIN (SELECT * FROM images ORDER BY image_id) AS `i` ON i.ad_id = a.id

How to order joined table without using temporary table? 🙂

Because it’s 5x slower than simple join:

RIGHT JOIN images AS `i` ON i.ad_id = a.id

And there are problems with fields list, which should be duplicated inside subquery as well to avoid using * sign.

Thanks 😉

Update

SELECT a.id, GROUP_CONCAT(image_id) AS `image_ids`
FROM `ads` AS `a`
RIGHT JOIN (SELECT * FROM images ORDER BY image_id) AS `i` ON i.ad_id = a.id
GROUP BY `a`.`id`
ORDER BY `a`.`id` DESC

There are multiple rows that match per id in joined table. That’s why i need to order them.

group_concat(image_id)

Answer 1

Order by image_id after the join.

(You do have an index on image_id, don’t you?)

UPDATE:

You can put the ORDER BY inside your GROUP_CONCAT:

GROUP_CONCAT(image_id ORDER BY image_id)

and then you don’t need the subquery.