Question

我有两张表users和select jobs_done, count(1) as number_of_users from ( select u.id, count(*) as jobs_done from jobs j JOIN users u on j.user_id = u.id group by u.id ) a group by jobs_done。用户与作业具有一对多的关系。

我想将用户划分为jobs_done组。换句话说，有多少用户做过1份工作，2份工作，3份工作等等以下查询就是这样做的。但是，我想将已完成3个或更多作业的所有用户整合到一个组中。

这是我目前的查询

times_used  number_of_users  
1           255  
2           100  
3           30  
4           10  
5           9

当前输出：

times_used  number_of_users  
1           255  
2           100  
3+          49

期望的输出：

{{1}}

Answer 1

您可以使用case表达式将值3+分组到一个大组中。这应该有效：

select
    case 
       when jobs_done >= 3 then '3+' 
       else cast(jobs_done as varchar(5)) 
    end as jobs_done,
    count(1) as number_of_users
from ( 
    select 
       u.id,
       count(*) as jobs_done
    from jobs j
    join users u on j.user_id = u.id 
    group by  u.id 
) a
group by case when jobs_done >= 3 then '3+' 
             else cast(jobs_done as varchar(5)) 
         end;

Answer 2

你可以基本上把所有东西分组。这是一个简单的例子：

test=# SELECT CASE WHEN x < 4 THEN x::text ELSE '4+' END AS y, 
              count(*) 
       FROM generate_series(1, 10) AS x 
       GROUP BY y 
       ORDER BY 1;
 y  | count 
----+-------
 1  |     1
 2  |     1
 3  |     1
 4+ |     7
(4 rows)

获得计数postgres的总数

2 个答案: