SQL request for several tables and operations in MySQL - php

Question

I have the following 3 tables: unit, stage, stats.
unit stage
+----+--------+ +----+-------+---------------------+
| id | status | | id |unit_id| date |
+----+--------+ +----+-------+---------------------+
| 1 | 2 | | 1 | 2 | 2013-11-22 00:00:00 |
| 2 | 3 | | 2 | 2 | 2013-11-26 12:00:00 |
| 3 | 3 | | 3 | 3 | 2013-10-11 00:00:00 |
| 4 | 0 | | 4 | 1 | 2013-12-29 00:00:00 |
+----+--------+ +----+-------+---------------------+
stats
+----+----------+---------------------+-------+
| id | stage_id | date | clicks|
+----+----------+---------------------+-------+
| 1 | 1 | 2013-11-22 00:00:00 | 10 |
| 2 | 1 | 2013-11-23 00:00:00 | 20 |
| 3 | 1 | 2013-11-24 00:00:00 | 25 |
| 4 | 2 | 2013-11-26 00:00:00 | 15 |
| 5 | 2 | 2013-11-27 12:00:00 | 21 |
| 6 | 3 | 2013-12-29 00:00:00 | 8 |
+----+----------+---------------------+-------+
I need a request, that will produce the following response:
+---------+---------------------+-----------------------+
| unit.id | stage.min.date | sum(stats.max.clicks) |
+---------+---------------------+-----------------------+
| 2 | 2013-11-22 00:00:00 | 46 |
| 3 | 2013-12-29 00:00:00 | 8 |
+---------+---------------------+-----------------------+
by the following rules:
1) unit.id - show only units with unit.status=3
2) stage.min.date - minimal stage.date for corresponding unit_id
3) sum(stats.max.clicks) - sum of stats.clicks with max dvalues for each stage_id associated with corresponding unit_id. In my example 46 = 25(stage_id=1) + 21(stage_id=2)
The problem is in min.date and sum of clicks - I have no idea how to get it in one query. Definitely it`s not a problem to do it using php code and several requests.
Schema in SQL Fiddle
Thanks in advance.

Answer 1

I just ask myself, why I do this? Your example resonse has an error, and does not match your fiddle... but:
SELECT
cc.unit_id, MIN(cc.date) as stage_min_date , SUM(dd.clicks) as stats_max_clicks
FROM
stage cc
LEFT JOIN (
SELECT
bb.stage_id, bb.clicks
FROM
stats bb LEFT JOIN (
SELECT id, stage_id, MAX(date) AS max_date
FROM stats
GROUP BY stage_id
) aa
ON
aa.max_date = bb.date
WHERE
aa.max_date IS NOT NULL
) dd
ON cc.id = dd.stage_id
LEFT JOIN unit ee
ON ee.id = cc.unit_id
WHERE ee.status = 3
GROUP BY cc.unit_id
...