Help, please make SQL select to database. There are such data.
id news_id season seria date_update
---|------|---------|-----|--------------------
1 | 4 | 1 | 7 | 2017-04-14 16:38:10
2 | 4 | 1 | 7 | 2017-04-14 17:38:10
5 | 4 | 1 | 7 | 2017-04-14 16:38:10
3 | 4 | 1 | 7 | 2017-04-14 16:38:10
4 | 4 | 1 | 7 | 2017-04-14 16:38:10
6 | 4 | 1 | 7 | 2017-04-14 16:38:10
7 | 4 | 1 | 7 | 2017-04-14 16:38:10
8 | 1 | 1 | 25 | 2017-04-23 18:42:00
Need to get all cells grouped by max season and seria and date and sorted by date_update DESC.
In result I need next rows
id news_id season seria date_update
---|------|---------|-----|--------------------
8 | 1 | 1 | 25 | 2017-04-23 18:42:00
2 | 4 | 1 | 7 | 2017-04-14 17:38:10
Because these rows have the highest season and seria and date_update per One news_id. i.e I need to select data which have highest season and seria and date_update grouped by news_id and also sorted by date_update DESC
I tried so, but the data is not always correct, and it does not always for some reason cover all the cells that fit the condition.
SELECT serial.*
FROM serial as serial
INNER JOIN (SELECT id, MAX(season) AS maxseason, MAX(seria) AS maxseria FROM serial GROUP BY news_id) as one_serial
ON serial.id = one_serial.id
WHERE serial.season = one_serial.maxseason AND serial.seria = one_serial.maxseria
ORDER BY serial.date_update
Please, help. Thanks.
The specification is unclear.
But we do know that the GROUP BY news_id clause is going collapse all of the rows with a common value of news_id into a single row. (Other databases would throw an error with this syntax; we can get MySQL to throw a similar error if we include ONLY_FULL_GROUP_BY in the sql_mode.)
My suggestion would be to remove the GROUP BY news_id clause from the end of the query.
But that's just a guess. It's not at all clear what you are trying to achieve.
EDIT
SELECT t.*
FROM (
SELECT r.news_id
, r.season
, r.seria
, MAX(r.date_update) AS max_date_update
FROM (
SELECT p.news_id
, p.season
, MAX(p.seria) AS max_seria
FROM (
SELECT n.news_id
, MAX(n.season) AS max_season
FROM serial n
GROUP BY n.news_id
) o
JOIN serial p
ON p.news_id = o.news_id
AND p.season = o.max_season
) q
JOIN serial r
ON r.news_id = q.news_id
AND r.season = q.season
AND r.seria = q.max_seria
) s
JOIN serial t
ON t.news_id = s.news_id
AND t.season = s.season
AND t.seria = s.seria
AND t.date_update = s.max_date_update
GROUP BY t.news_id
ORDER BY t.news_id
Or, an alternate approach making use of MySQL user-defined variables...
SELECT s.id
, s.season
, s.seria
, s.date_update
FROM (
SELECT IF(q.news_id = @p_news_id,0,1) AS is_max
, q.id
, @p_news_id := q.news_id AS news_id
, q.season
, q.seria
, q.date_update
FROM ( SELECT @p_news_id := NULL ) r
CROSS
JOIN serial q
ORDER
BY q.news_id DESC
, q.season DESC
, q.seria DESC
, q.date_update DESC
) s
WHERE s.is_max
ORDER BY s.news_id