如何在Oracle中查詢列值的分佈（按值範圍分組）？

Question

假設在Oracle中有一個名爲DISTANCES的表，名爲distance的浮點類型列。距離範圍是[0，1000]。我想知道距離的分佈，例如，在以下每個範圍中有多少行：[0,10]，（10,50），（50,100]，（100,500），.. 。？（5000，10000]

如何建立這個SQL查詢

Answer 1

使用派生表把每個距離到它的組，然後GROUP BY和count：

select dist_group, count(*) 
from 
(
select case when distance between 0 and 10 then '(0, 10)' 
      when distance between 10 and 50 then '(10, 50)' 
      ... 
      when distance between 5000 and 10000 then '(5000, 10000)' end as dist_group 
from distances 
) 
group by dist_group 

Answer 2

SELECT COUNT(CASE WHEN 0 <= distance AND distance <= 10 THEN distance END) AS in_range_0_10, 
     COUNT(CASE WHEN 10 < distance AND distance <= 50 THEN distance END) AS in_range_10_50, 
     COUNT(CASE WHEN 50 < distance AND distance <= 100 THEN distance END) AS in_range_50_100, 
     COUNT(CASE WHEN 100 < distance AND distance <= 500 THEN distance END) AS in_range_100_500, 
     COUNT(CASE WHEN 500 < distance AND distance <= 1000 THEN distance END) AS in_range_500_1000 
FROM Distance;