按计数 sql 分组

Posted 2023-05-08

【中文标题】按计数 sql 分组

【英文标题】：group by count sql

【发布时间】：2021-09-30 09:39:23

【问题描述】：

我有一个脚本

SELECT  customer_id, COUNT(*)
FROM devices 
GROUP BY customer_id
ORDER BY 2 desc;

结果是

customer_id      count
1234              8
4567              7
8910              7
1112              7
1314              5
1516              5

但我期待的是

devices      customer
8              1
7              3
5              2

有什么办法不使用新表？

【参考方案1】：

使用您当前的查询作为另一个查询的来源：

with temp as
  -- this is your current query
  (select customer_id, 
          count(*) cnt
   from devices
   group by customer_id
  )
select cnt as devices, 
       count(*) as customer
from temp
group by cnt;

【参考方案2】：

count(*) 的通常用途是找出许多行已通过 group 函数聚合。想让你蚂蚁做的是在第二次选择中汇总你的结果，然后再次询问 count(*) 以获得你描述的结果。

【讨论】：

我试过 ``` SELECT customer_id, COUNT(1) FROM ( SELECT customer_id, COUNT(*) FROM devices GROUP BY customer_id ORDER BY 2 desc; ) devices GROUP BY customer_id ``` 它它不起作用