mysql按天分组并计数，然后每天仅过滤最大值

Question

I'm stuck on this query. I need to do a group by date, card_id and only show the highest hits. I have this data:

date        card_name     card_id   hits
29/02/2016  Paul Stanley    1345    12
29/02/2016  Phil Anselmo    1347    16
25/02/2016  Dave Mustaine   1349    10
25/02/2016  Ozzy            1351    17
23/02/2016  Jhonny Cash     1353    13
23/02/2016  Elvis           1355    15
20/02/2016  James Hethfield 1357    9
20/02/2016  Max Cavalera    1359    12

My query at the moment

SELECT DATE(card.create_date) `day`, `name`,card_model_id, count(1) hits
FROM card
Join card_model ON card.card_model_id = card_model.id
WHERE DATE(card.create_date) >= DATE(DATE_SUB(NOW(), INTERVAL 1 MONTH)) AND card_model.preview = 0
GROUP BY  `day`, card_model_id 
;

I want to group by date, card_id and filter the higher hits result showing only one row per date. As if I run a max(hits) with group by but I won't work

Like:

date        card_name     card_id   hits
29/02/2016  Phil Anselmo    1347    16
25/02/2016  Ozzy            1351    17
23/02/2016  Elvis           1355    15
20/02/2016  Max Cavalera    1359    12

Any light on that will be appreciated. Thanks for reading.

Answer 1

Here is one way to do this. Based on your sample data (not the query):

select s.*
from sample s
where s.hits = (select max(s2.hits)
                from sample s2
                where date(s2.date) = date(s.date)
               );

Your attempted query seems to have no relationship to the sample data, so it is unclear how to incorporate those tables (the attempted query has different columns and two tables).