MySQL按rand()按天分组 [英] MySQL order by rand() grouped by day

问题描述

是否可以在同一天内获得随机物品?

Is it possible to get random items inside the same day?

例如:

+----+---------------------+  
| id | md                  |  
+----+---------------------+  
|  1 | 2010-06-27 11:26:01 |  
|  2 | 2010-06-27 11:28:20 |  
|  3 | 2010-06-27 11:29:46 |  
|  4 | 2010-06-27 11:30:50 |  
|  5 | 2010-06-27 12:20:56 |  
|  6 | 2010-06-27 12:27:42 |  
|  7 | 2010-06-27 15:14:05 |  
|  8 | 2010-07-06 01:53:33 |  
|  9 | 2010-07-06 01:52:52 |  
+----+---------------------+  

我想在同一天内随机挑选物品，但同时我希望按日期desc对其进行排序.像这样:

I want to pick random items inside the same day, but at same time i want it ordered by date desc. Something like this:

+----+---------------------+  
| id | md                  |  
+----+---------------------+  

|  8 | 2010-07-06 01:53:33 |  random block  
|  9 | 2010-07-06 01:52:52 |  

|  2 | 2010-06-27 11:28:20 |  random block  
|  4 | 2010-06-27 11:30:50 |  
|  1 | 2010-06-27 11:26:01 |  
|  6 | 2010-06-27 12:27:42 |  
|  3 | 2010-06-27 11:29:46 |  
|  5 | 2010-06-27 12:20:56 |  
|  7 | 2010-06-27 15:14:05 |  

+----+---------------------+  

不知道如何开始，或者甚至不可能，因为rand()的订单不接受分组.

No idea how to start or if this is even possible since order by rand() won't accept grouping.

推荐答案

可能不是很有效，但是请尝试

Probably not very efficient, but try

select * from (select * from tbl order by rand()) as t group by date(md)

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