MySQL的 - 查詢 - DISTINCT與羣體之間的混合BY

Question

我有如下表：

SELECT * FROM tblTemp; 
+-----+---------------------+ 
| id | timestamp   | 
+-----+---------------------+ 
| 84 | 2013-07-18 22:36:32 | 
| 85 | 2013-07-18 22:36:33 | 
| 88 | 2013-07-18 22:36:33 | 
| 89 | 2013-07-18 22:36:34 | 
| 263 | 2013-08-04 16:01:05 | 
| 264 | 2013-08-04 16:01:11 | 
| 272 | 2013-08-04 16:01:42 | 
| 273 | 2013-08-04 16:01:42 | 
| 274 | 2013-08-04 16:01:42 | 
| 275 | 2013-08-04 16:21:25 | 
| 276 | 2013-08-04 16:21:25 | 
| 279 | 2013-08-04 16:21:26 | 
| 280 | 2013-08-04 16:21:27 | 
| 281 | 2013-08-04 16:21:27 | 
+-----+---------------------+ 
14 rows in set (0.00 sec) 

首先我想刪除所有雙戳在視圖中這樣

SELECT DISTINCT timestamp FROM tblTemp; 
+---------------------+ 
| timestamp   | 
+---------------------+ 
| 2013-07-18 22:36:32 | 
| 2013-07-18 22:36:33 | 
| 2013-07-18 22:36:34 | 
| 2013-08-04 16:01:05 | 
| 2013-08-04 16:01:11 | 
| 2013-08-04 16:01:42 | 
| 2013-08-04 16:21:25 | 
| 2013-08-04 16:21:26 | 
| 2013-08-04 16:21:27 | 
+---------------------+ 
9 rows in set (0.00 sec) 

但這不是足夠。我需要的數量，有多少項是在DB的每個小時（不重複） - 關於：

+---------------------+-------+ 
| timestamp   | count | 
+---------------------+-------+ 
| 2013-07-18 22:00:00 | 3  | 
| 2013-08-04 16:00:00 | 6  | 
+---------------------+-------| 

首先，我想我可以使用下面的命令：

SELECT timestamp, COUNT(id) FROM tblTemp GROUP BY YEAR(timestamp), MONTH(timestamp), DAY(timestamp), HOUR(timestamp) 

但它不」工作正常。命令計數所有行：/

+---------------------+-------+ 
| timestamp   | count | 
+---------------------+-------+ 
| 2013-07-18 22:36:32 |  4 | 
| 2013-08-04 16:01:05 | 10 | 
+---------------------+-------+ 

這並不重要，如果在列時間戳值是2013年7月18日22:00:00或2013年7月18日22點36分32秒或其他任何只要時間和日期是可識別的。

謝謝:)

Answer 1

也許這樣的事情（你可能需要檢查的日期格式字符串）

SELECT DATE_FORMAT(timestamp,'%m/%d/%Y %H') timestamp, COUNT(id) 
FROM tblTemp 
GROUP BY DATE_FORMAT(timestamp,'%m/%d/%Y %H') 

Answer 2

select DATE_FORMAT(`timestamp`, '%Y-%m-%d %H'), count(*) 
from (select distinct `timestamp` from Table1) abc 
group by DATE_FORMAT(`timestamp`, '%Y-%m-%d %H'); 

fiddle

Answer 3

SELECT DATE_FORMAT(timestamp,'%m/%d/%Y %H') AS date_hour, 
    COUNT(DISTINCT timestamp) 
FROM tblTemp 
GROUP BY date_hour 

見http://dev.mysql.com/doc/refman/5.6/en/group-by-functions.html#function_count-distinct