Switching Raw greatest-n-per-group MySQL query to Laravel query builder - mysql

Question

I want to move a raw mysql query into Laravel 4's query builder, or preferably Eloquent.
The Setup
A database for storing discount keys for games.
Discount keys are stored in key sets where each key set is associated with one game (a game can have multiple keysets).
The following query is intended to return a table of key sets and relevant data, for viewing on an admin page.
The 'keys used so far' is calculated by a scheduled event and periodically stored/updated in log entries in a table keySetLogs. (it's smart enough to only log data when the count changes)
We want to show the most up-to-date value of 'keys used', which is a 'greatest-n-per-group' problem.
The Raw Query
SELECT
`logs`.`id_keySet`,
`games`.`name`,
`kset`.`discount`,
`kset`.`keys_total`,
`logs`.`keys_used`
FROM `keySets` AS `kset`
INNER JOIN
(
SELECT
`ksl1`.*
FROM `keySetLogs` AS `ksl1`
LEFT OUTER JOIN `keySetLogs` AS `ksl2`
ON (`ksl1`.`id_keySet` = `ksl2`.`id_keySet` AND `ksl1`.`set_at` < `ksl2`.`set_at`)
WHERE `ksl2`.`id_keySet` IS NULL
ORDER BY `id_keySet`
)
AS `logs`
ON `logs`.`id_keySet` = `kset`.`id`
INNER JOIN `games`
ON `games`.`id` = `kset`.`id_game`
ORDER BY `kset`.`id_game` ASC, `kset`.`discount` DESC
Note: the nested query gets the most up-to-date keys_used value from the logs. This greatest-n-per-group code used as discussed in this question.
Example Output:
+-----------+-------------+----------+------------+-----------+
| id_keySet | name | discount | keys_total | keys_used |
+-----------+-------------+----------+------------+-----------+
| 5 | Test_Game_1 | 100.00 | 10 | 4 |
| 6 | Test_Game_1 | 50.00 | 100 | 20 |
| 3 | Test_Game_2 | 100.00 | 10 | 8 |
| 4 | Test_Game_2 | 50.00 | 100 | 14 |
| 1 | Test_Game_3 | 100.00 | 10 | 1 |
| 2 | Test_Game_3 | 50.00 | 100 | 5 |
...
The Question(s)
I have KeySet, KeySetLog and Game Eloquent Models created with relationship functions set up.
How would I write the nested query in query builder?
Is it possible to write the query entirely with eloquent (no manually writing joins)?

Answer 1

I don't know Laravel or Eloquent so I probably shouldn't comment, but if performance isn't at stake then it seems to me that this query could be rewritten something like this:
SELECT ksl1.id_keySet
, g.name
, k.discount
, k.keys_total
, ksl1.keys_used
FROM keySetLogs ksl1
LEFT
JOIN keySetLogs ksl2
ON ksl1.id_keySet = ksl2.id_keySet
AND ksl1.set_at < ksl2.set_at
LEFT
JOIN keysets k
ON k.id = l.id_keySet
LEFT
JOIN games g
ON g.id = k.id_game
WHERE ksl2.id_keySet IS NULL
ORDER
BY k.id_game ASC
, k.discount DESC