根据条件选择列

Question

我有一个类似于以下的表格：

+---------+--------------+
| user_id | distance     |
+---------+--------------+
|     101 | 12.05        |
|     103 | 4.8          |
|     207 | 37.1         |
|     991 | 3.51         |
|     215 | 15.9         |
+---------+--------------+

然后我想要覆盖不同距离范围的用户数量：0-5km as short_distance, 5-10km as medium_distance, >10km as long_distance。

我在汇总时有点困惑。

Answer 1

使用 CASE 表达式：

select user_id, 
       case 
         when distance <= 5 then 'short distance'
         when distance <= 10 then 'medium distance'
         else 'long distance'
       end as what
from the_table;

Answer 2

您希望明智地计算用户类别。试试这个

select 
       case 
         when distance > 10 then 'long_distance'
         when distance > 5  then 'medium_distance'
         else 'short_distance'
      end as "distance_type", count(*) as "Count"
from user_distance

group by "distance_type"

DEMO