MySQL GROUP BY grouping by lowest field value - mysql

Question

I'm trying to fetch the lowest price per day per hotel, I get multiple results.
I first try to fetch the lowest amount with the MIN() function, then inner join.
When i later try to group by outside the subquery, it just groups by the lowest id.
The SQL itself:
SELECT mt.id, mt.amount, mt.fk_hotel, mt.start_date
FROM price mt
INNER JOIN
(
SELECT price.id, MIN(price.amount) minAmount
FROM price
WHERE 1=1 AND price.start_date >= '2014-10-08' AND price.start_date <= '2014-10-10' AND price.active = 1 AND price.max_people = 2
GROUP BY id
) t
ON mt.id = t.id AND mt.amount = t.minAmount
ORDER BY mt.fk_hotel, mt.amount;
And the results looks like this:
http://jsfiddle.net/63mg3b2j/
I want to group by the start date and fk_hotel so that it groups by the lowest amount value, can anybody help me? Am I being clear?
Edit: I also need a field fk_room from the corresponding row, so i can inner join

Answer 1

Try this:
SELECT MIN(mt.amount) AS min_amount, mt.fk_hotel, mt.start_date
FROM price mt
WHERE
mt.active = 1 AND
mt.max_people = 2 AND
mt.start_date >= '2014-10-08' AND mt.start_date <= '2014-10-10'
GROUP BY mt.fk_hotel, mt.start_date
ORDER BY mt.fk_hotel, min_amount;

Answer 2

Well first of all get a table with minimum value in top row using ORDER BY and then GROUP BY for your required result
SELECT mt.id, mt.amount, mt.fk_hotel, mt.start_date
FROM
(SELECT id, amount, fk_hotel, start_date
FROM price
WHERE start_date >= '2014-10-08' AND start_date <= '2014-10-10'
AND active = 1 AND max_people = 2
ORDER BY amount DESC) AS mt
GROUP BY mt.id

Answer 3

Well I had to still go with a subquery, cause i needed some additional foreign key fields from the corresponding row to inner join some other stuff. It isn't a great solution, cause it fetches too much stuff, the rest is filtered out programmatically.
The most annoying thing here, when I try to use MIN() or MAX() function and get the appropriate fields to that row, it fetches the first results from the DB, which are incorrect and so i have to use a subquery to inner join to get the other fields, I can use grouping, but I had too many fields to group. Maybe I'm missing something. The amount of data doesn't grow in time, so I guess it works for me. So this is the final SQL i came up with, for future reference..
SELECT mt.*, roomtype.name roomname, hotel.name hotelname
FROM booking.price mt
INNER JOIN roomtype ON roomtype.id = mt.fk_roomtype
INNER JOIN hotel ON hotel.id = mt.fk_hotel
INNER JOIN(
SELECT price.id, MIN(price.amount) minAmount
FROM booking.price WHERE 1=1 AND price.start_date >= '2014-10-22' AND price.start_date <= '2014-10-31' AND price.max_people = 2 AND price.active = 1
GROUP BY id
) t
ON mt.id = t.id AND mt.amount = t.minAmount
ORDER BY mt.start_date, mt.amount