MySQL query for distinct rows on count - mysql

Question

I have such query that gives me results about bestseller items from shops, at the moment it works fine, but now I want to get only one product from each shop so to have a distinct si.shop_id only one bestseller product from a shop
SELECT `si`.`id`, si.shop_id,
(SELECT COUNT(*)
FROM `transaction_item` AS `tis`
JOIN `transaction` as `t`
ON `t`.`id` = `tis`.`transaction_id`
WHERE `tis`.`shop_item_id` = `si`.`id`
AND `t`.`added_date` >= '2014-02-26 00:00:00')
AS `count`
FROM `shop_item` AS `si`
INNER JOIN `transaction_item` AS `ti`
ON ti.shop_item_id = si.id
GROUP BY `si`.`id`
ORDER BY `count` DESC LIMIT 7
and that gives mu a result like:
+--------+---------+-------+
| id | shop_id | count |
+--------+---------+-------+
| 425030 | 38027 | 111 |
| 291974 | 5368 | 20 |
| 425033 | 38027 | 18 |
| 291975 | 5368 | 12 |
| 142776 | 5368 | 10 |
| 397016 | 38027 | 9 |
| 291881 | 5368 | 8 |
+--------+---------+-------+
any ideas?
EDIT
so I created a fiddle for it
http://sqlfiddle.com/#!2/cfc4c/1
Now the query returns best selling products I want it to return only one product from shopso the result of fiddle should be
+----+---------+-------+
| ID | SHOP_ID | COUNT |
+----+---------+-------+
| 1 | 222 | 3 |
| 4 | 333 | 2 |
| 8 | 555 | 1 |
| 9 | 777 | 1 |
+----+---------+-------+

Answer 1

Possibly something like this:-
SELECT si.shop_id,
SUBSTRING_INDEX(GROUP_CONCAT(CONCAT_WS(':', si.id, sub1.item_count) ORDER BY sub1.item_count DESC), ',', 1) AS `count`
FROM shop_item AS si
INNER JOIN
(
SELECT tis.shop_item_id, COUNT(*) AS item_count
FROM transaction_item AS tis
JOIN `transaction` as t
ON t.id = tis.transaction_id
AND t.added_date >= '2014-02-26 00:00:00'
GROUP BY tis.shop_item_id
) sub1
ON sub1.shop_item_id = si.id
GROUP BY si.shop_id
ORDER BY `count` DESC LIMIT 7
The sub query gets the count of items for each shop. Then the main query concatenates the item id and the item count together, group concatenates all those for a single shop together (ordered by the count descending) and then uses SUBSTRING_INDEX to grab the first one (ie, everything before the first comma).
You will have to split up the count field to get the item id and count separately (the separator is a : ).
This is taking a few guesses about what you really want, and with no table declares or data it isn't tested.
EDIT - now tested with the SQL fiddle example:-
SELECT SUBSTRING_INDEX(`count`, ':', 1) AS ID,
shop_id,
SUBSTRING_INDEX(`count`, ':', -1) AS `count`
FROM
(
SELECT si.shop_id,
SUBSTRING_INDEX(GROUP_CONCAT(CONCAT_WS(':', si.id, sub1.item_count) ORDER BY sub1.item_count DESC), ',', 1) AS `count`
FROM shop_item AS si
INNER JOIN transaction_item AS ti
ON ti.shop_item_id = si.id
INNER JOIN
(
SELECT tis.shop_item_id, COUNT(*) AS item_count
FROM transaction_item AS tis
JOIN `transaction` as t
ON t.id = tis.transaction_id
AND t.added_date >= '2014-02-26 00:00:00'
GROUP BY tis.shop_item_id
) sub1
ON sub1.shop_item_id = si.id
GROUP BY si.shop_id
) sub2
ORDER BY `count` DESC LIMIT 7;