SQL從「自定義」 post_type計數的用戶自定義post_type的個體數量

Question

我想獲取X最後的條目，如果可能的話在一個查詢來獲取：

• 最後4個不同的用戶
• 排除'ID' = '1'
WITH post_type
• = 'custom'
• 通過date或ID（DESC）
• 計數 '自定義' PO的總數目有序st_type爲每個用戶（COUNT（））

這裏是一個數據例如：

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" 

，我有不完整的查詢：

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

排序方式ID是這裏類似比通過date訂購。 沒有GROUP BY 'user'這個工作，但問題是，我想避免在這個選擇2個'自定義'發佈一個用戶：我需要選擇4個不同的用戶。 所以我的問題是GROUP BY。

我該如何解決這個問題？

最後一件事：
是否有可能與COUNT()，本次評選共統計「自定義」的帖子爲每個用戶，並在新列返回值？

Answer 1

試試這個;）

查詢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 

入住這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 | 

子查詢t2將得到最大ID在每個用戶在user != '1' and post_type = 'custom' ，然後inner join t1與t1.ID = t2.ID and t1.user = t2.user上的t2將得到我們最多ID的記錄，其中每個user在表post中。如：「2783」，「2759」，「2757」，「2683」，「2681」，「2652」，「2630」，「2617」，「2596」，「2215」。

最後是order by和limit，當然你可以得到「2783」，「2759」，「2757」，「2683」。希望我沒有把你的問題搞錯。

Answer 2

您可以使用變量的查詢，以獲得最後4個用戶的用戶ID：

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 

該查詢返回以下值：

user 
---- 
5 
3 
12 
15 

使用上面的查詢作爲一個子查詢，你可以得到預期的結果：

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

輸出：

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

Demo here