按降序按顺序选择不同的行

Question

我有一张表hastags

id|tweet_id|  tag   |time
1   1       hell   
2   2       hellyeah    
3   3       hell
4   4       stackoverflow
5   5       hell   
6   6       hellyeah    
7   7       bellrings
8   7       nomorehell
8   7       nomorehell

我想在特定时间之上选择最常用的 tags的数量。 现在，如果我将查询限制为3行，我应该

|tag    | count|
hell        3
hellyeah    2
nomorehell  2 

如何帮助我实现这一目标？

Answer 1

SELECT tag, count(*) as anz FROM hastags GROUP BY tag ORDER BY anz DESC

Answer 2

我选择2014-12-29作为特定时间的示例

select tag, 
       sum(`time` > '2014-12-29') as sum_greater,
       sum(`time` < '2014-12-29') as sum_smaller
from hashtags
group by tag
order by sum_greater desc, sum_smaller desc
limit 3

Answer 3

考虑到开始时间和结束时间，则此查询将起作用。

SELECT tag, count(tag) FROM hastags where (start <= end and :time >= start and :time <= end) or
  (end < start and (:time <= end or :time >= start)) GROUP BY tag;