SQL Get X last entries from a 'custom' post_type counting users individual number of custom post_type

问题

I would like, if possible to get in one query:

The last 4 different users
Excluding 'ID' = '1'
WITH post_type = 'custom'
Ordered by date or ID (DESC)
Counting the total number of 'custom' post_type for each user (COUNT())

Here is a data example:

Table Name: 'post'

   ID   |  user |           Date            |    title      |     status    |    post_type
        |       |                           |               |               |   
"2785"  |   "1" |   "2016-05-24 18:49:15"   |   "Title"     |   "published" |   "page_post"
"2783"  |   "5" |   "2016-05-24 11:24:08"   |   "Title"     |   "published" |   "custom"
"2781"  |   "1" |   "2016-05-18 20:40:11"   |   "Title"     |   "published" |   "custom"
"2759"  |   "3" |   "2016-05-07 14:00:22"   |   "Title"     |   "published" |   "custom"
"2757"  |  "12" |   "2016-05-02 12:41:00"   |   "Title"     |   "published" |   "custom"
"2756"  |   "1" |   "2016-04-30 22:47:07"   |   "Title"     |   "published" |   "custom"
"2755"  |   "5" |   "2016-04-29 13:54:21"   |   "Title"     |   "published" |   "blog_post"
"2754"  |   "1" |   "2016-04-29 11:33:36"   |   "Title"     |   "published" |   "page_post"
"2738"  |   "3" |   "2016-05-06 12:45:58"   |   "Title"     |   "published" |   "custom"
"2736"  |  "12" |   "2016-04-24 17:17:04"   |   "Title"     |   "published" |   "custom"
"2683"  |  "15" |   "2016-04-22 20:27:45"   |   "Title"     |   "published" |   "custom"
"2681"  |  "18" |   "2016-04-21 00:20:55"   |   "Title"     |   "published" |   "custom"
"2671"  |   "1" |   "2016-04-11 18:38:57"   |   "Title"     |   "published" |   "other_post"
"2652"  |   "4" |   "2016-04-02 17:43:41"   |   "Title"     |   "published" |   "custom"
"2651"  |   "5" |   "2016-03-28 17:12:00"   |   "Title"     |   "published" |   "custom"
"2639"  |  "18" |   "2016-03-22 14:58:00"   |   "Title"     |   "published" |   "custom"
"2630"  |  "19" |   "2016-03-21 15:27:00"   |   "Title"     |   "published" |   "custom"
"2617"  |  "14" |   "2016-03-17 12:22:06"   |   "Title"     |   "published" |   "custom"
"2616"  |   "5" |   "2016-03-16 15:23:00"   |   "Title"     |   "published" |   "page_post"
"2598"  |   "4" |   "2016-03-14 15:27:29"   |   "Title"     |   "published" |   "custom"
"2596"  |   "2" |   "2016-03-10 17:43:00"   |   "Title"     |   "published" |   "custom"
"2571"  |   "1" |   "2016-03-09 14:19:31"   |   "Title"     |   "published" |   "blog_post"
"2250"  |  "19" |   "2016-02-29 12:15:48"   |   "Title"     |   "published" |   "custom"
"2249"  |  "15" |   "2016-02-29 09:45:35"   |   "Title"     |   "published" |   "custom"
"2215"  |  "13" |   "2016-02-22 18:21:54"   |   "Title"     |   "published" |   "custom"
"2201"  |   "3" |   "2016-02-15 17:40:00"   |   "Title"     |   "published" |   "custom"
"1914"  |   "2" |   "2015-11-13 12:08:00"   |   "Title"     |   "published" |   "other_post"

The incomplete query that I have:

SELECT *
FROM 'posts' 
WHERE 'user' != 1 AND 'post_type' = 'custom_type' 
GROUP BY 'user' 
ORDER BY 'ID' DESC LIMIT 4

Ordering by ID is similar here than ordering by date. Without GROUP BY 'user' this works, but the problem is that I want to avoid in this selection 2 'custom' post for one user: I need a selection of 4 different users. So my problem is GROUP BY.

How can I solve this issue?

Last thing:
Is it possible with COUNT(), counting total 'custom' posts for each user in this selection, and returning the value in a new column?

回答1:

Try this;)

Query 1:

select t1.*, t2.userCnt
from `posts` t1
inner join (
    select max(`ID`) as `ID`, `user`, count(1) as userCnt
    from `posts`
    where `user` != '1'
    and `post_type` = 'custom'
    group by `user`
) t2 on t1.`ID` = t2.`ID` and t1.`user` = t2.`user`
order by t1.`ID` desc limit 4

Check this SqlFiddle Results:

|   ID | user |                Date | title |    status | post_type | userCnt |
|------|------|---------------------|-------|-----------|-----------|---------|
| 2783 |    5 | 2016-05-24 11:24:08 | Title | published |    custom |       2 |
| 2759 |    3 | 2016-05-07 14:00:22 | Title | published |    custom |       3 |
| 2757 |   12 | 2016-05-02 12:41:00 | Title | published |    custom |       2 |
| 2683 |   15 | 2016-04-22 20:27:45 | Title | published |    custom |       2 |

Subquery t2 will get the max ID in each user when user != '1' and post_type = 'custom', then inner join t1 with t2 on t1.ID = t2.ID and t1.user = t2.user will get us record which has max ID by each user in table post. Like : "2783", "2759", "2757", "2683", "2681", "2652", "2630" , "2617", "2596", "2215".

And last with order by and limit, of course you can get "2783", "2759", "2757", "2683". Hope I did not mistake your question.

回答2:

You can use a query with variables, so as to get the user ids of the last 4 users:

SELECT DISTINCT `user`
FROM (
  SELECT user,  
         @cnt := IF(FIND_IN_SET(`user`, @uid) > 0, @cnt,
                    IF(@uid := CONCAT(@uid, ',', CAST(`user` AS CHAR(4))),
                       @cnt + 1, @cnt + 1)) AS cnt
  FROM posts
  CROSS JOIN (SELECT @cnt := 0, @uid := '') AS vars
  WHERE `user` != 1  AND `post_type` = 'custom'
  ORDER BY ID DESC) AS t
WHERE t.cnt <= 4

This query returns the following values:

user
----
5
3
12
15

Using the above query as a subquery, you can get the expected result with:

SELECT `user`, SUM(`post_type` = 'custom') AS cnt
FROM posts
WHERE `user` IN (... above query goes here ...)
GROUP BY `user`

Output:

user | cnt
-----+-----
 3   | 3
 5   | 4
 12  | 2
 15  | 2

Demo here

来源：https://stackoverflow.com/questions/37694182/sql-get-x-last-entries-from-a-custom-post-type-counting-users-individual-numbe

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mysql

sql

count

group-by

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