mysql - MySQL - 按范围分组

Question

我需要计算值范围内的记录。

例如：对于集合1, 7, 9, 23, 33, 35, 1017

select count(myvalue) group by round(myvalue / 10)给出类似的东西：

0-10  -> 3
10-20 -> 0
20-30 -> 1
30-40 -> 2
1010-1020 -> 1

这工作正常。但是，我需要设置一个上限，以便 MySQL 返回40+ --> 1？如何实现？

Answer 1

您可以对客户端的值求和，也可以使用两个查询（可能带有union）来获取数据，例如：

select round(myvalue / 10), count(myvalue) from table where myvalue < 40 group by round(myvalue / 10)
union
select '40+', count(myvalue) from table where myvalue >= 40

绝对可以将它写在带有子查询或复杂条件的单个查询中，但它不会那么简单和可维护。

Answer 2

select t.myvalue as [range], count(*) as [occurences]
from (
  select myvalue,
   case when myvalue >= 0 and myvalue< 10 then '0-9'
   when myvalue >= 10 and myvalue< 20 then '10-19'
   when myvalue >= 20 and myvalue< 20 then '20-29'
   when myvalue >= 30 and myvalue< 40 then '30-39'
   else '40+' end as range
 from t) t
group by t.myvalue

Answer 3

我建议这个解决方案借鉴了 pilsetnieks 和 Jayram 的解决方案：

SELECT
    COUNT(*) AS cnt,
    IF (myvalue >= 40; -1; ROUND(myvalue / 10) AS range
FROM t
GROUP BY range

Answer 4

SELECT case 
   when myvalue >= 0 and myvalue< 10 then '0-9'
   when myvalue >= 10 and myvalue< 20 then '10-19'
   when myvalue >= 20 and myvalue< 20 then '20-29'
   when myvalue >= 30 and myvalue< 40 then '30-39'
   else '40+' 
   end as range
 from t 
group by range