Doing complex ordering with a MySQL query - mysql

Question

I'm having trouble with a Mysql Query that require some "complex" ordering.
I've 2 tables:
Training
+--------------+------------------+
| training_id | training_name |
+--------------+------------------+
| 1 | test1 |
| 2 | test2 |
| 3 | test3 |
+--------------+------------------+
Training_venue
+----------+--------------+------------+
| venue_id | training_id | venue_date |
+----------+--------------+------------+
| 1 | 2 | 2009-06-01 |
| 2 | 2 | 2012-06-01 |
| 3 | 2 | 2011-06-01 |
| 4 | 1 | 2009-09-01 |
| 5 | 1 | 2011-09-01 |
| 6 | 1 | 2012-09-01 |
| 7 | 3 | 2009-01-01 |
+----------+--------------+------------+
And I'm expecting the following results:
+--------------+------------------+------------+--------------+
| training_id | training_name | venue_id | venue_date |
+--------------+------------------+------------+--------------+
| 2 | test2 | 2 | 2011-06-01 |
| 2 | test2 | 3 | 2012-06-01 |
| 1 | test1 | 6 | 2011-09-01 |
| 1 | test1 | 5 | 2012-09-01 |
+--------------+------------------+------------+--------------+
As you can see, the result requirement are:
A training with no future venue is discarded.
Expired venue are discarded
The trainings are "grouped" together
The trainings with the soonest venue is first, the training with the "latest soonest venue" is last
Inside the training, the venues are ordered from the soonest to the latest.
What mysql query will return that result set ?
Edit:
Here's what I've tried so far:
SELECT *
FROM `training` AS t
LEFT JOIN `training_venue` AS v USING ( `training_id` )
WHERE `venue_date` >= NOW()
ORDER BY `training_id;
But if the order by training_id take care of keeping all the training "grouped" together, it doesnt permit to order the training from the training with the soonest venue to the training with the lastest venue.
I also edited the data table to illustrate that problematic. See how the results are ordered, it's not by training_id, but by soonest venue.
Edit:
Corrected the dates.

Answer 1

SELECT t1.training_id, t1.training_name, t2.venue_id, t2.venue_date
FROM Training t1
INNER JOIN Training_venue t2 ON t1.training_id = t2.training_id
WHERE t2.venue_date >= NOW()
ORDER BY t1.training_id ASC, t2.venue_date ASC
I don't know what your last point is getting at: "Inside the training, the venues are ordered from the soonest to the latest." But the above query seems to match the rest of your needs.
EDIT: I now sort of understand better what you are after. And it is a tad complicated I think. I'll have another think about it.
EDIT: I think I have it!
SELECT t1.training_id, t1.training_name, t2.venue_id, t2.venue_date
FROM Training t1
INNER JOIN (SELECT training_id, venue_date
FROM training_venue
WHERE venue_date >= NOW()
GROUP BY training_id
ORDER BY MIN(venue_date)) t3 ON t1.training_id = t3.training_id
INNER JOIN Training_venue t2 ON t1.training_id = t2.training_id
WHERE t2.venue_date >= NOW()
ORDER BY t3.venue_date DESC, t2.venue_date ASC
Try it!
EDIT: Was using '2010-01-01' instead of NOW() as NOW() would lose the 2010 dates that you seemed to want included.