Question

我有以下表格数据：

value
1
5
10.5
12
36

我想将这些值映射到：

range      avg
0-21       (1 + 5 + 10.5 + 12) / 4
21.001-34  0
34.001-64  36
64 +       0

基本上将每个值映射到范围，并计算每个范围内所有值的平均值。

我试图做：

select 
case
when avggeneral between 0 and 21 then ' 0-21'
when avggeneral between 21.00001 and 34 then ' 21-34'
when avggeneral between 34.00001 and 64 then ' 34-64'
else '64+'
end as 'range',
AVG(*) as 'avg'
from table

但这不起作用...我不知道如何制作静态范围...

如何在MySQL中做到这一点？

方法应为： 1.将值映射到这些组中（0-21、21-34等。） 2.计算每组的AVG。

上面示例的期望输出是这样的：

range      avg
0-21       7.125
21.001-34  0
34.001-64  36
64 +       0

range列是静态的。始终带有5行。 avg列是动态的。.值是value列的实际AVG。

Answer 1

您可以使用UNION ALL和LEFT JOIN来建立范围列表：

SELECT CONCAT(IFNULL(ranges.min, '∞'), '-', IFNULL(ranges.max, '∞')) AS `range`, avg(value) AS avg
FROM (
    SELECT 0 AS min, 21 AS max UNION ALL
    SELECT 21, 34 UNION ALL
    SELECT 34, 64 UNION ALL
    SELECT 64, NULL
) AS ranges
LEFT JOIN t ON (ranges.min IS NULL OR value >= ranges.min) AND
               (ranges.max IS NULL OR value <  ranges.max)
GROUP BY ranges.min, ranges.max

请注意，上面的查询会将20.9999放在[0-21)范围内，并将21.0000放在[21-34)范围内。

Answer 2

您可以使用UNION来获得所需的结果，如下所示：

select '0-21' as Range1, coalesce(avg(avggeneral),0) as AVG from Table1
where avggeneral > 0 and avggeneral <= 21
union
select '21-34' as Range1, coalesce(avg(avggeneral),0) as AVG from Table1
where avggeneral > 21 and avggeneral <= 34
union
select '34-64' as Range1, coalesce(avg(avggeneral),0) as AVG from Table1
where avggeneral > 34 and avggeneral <= 64
union
select '64+' as Range1, coalesce(avg(avggeneral),0) as AVG from Table1
where avggeneral > 64

SQL HERE

Answer 3

您实际上不需要使用这些小数。
因为例如，如果“值”等于21，则CASE在评估下一个WHEN之前将已经返回0-21范围。

但是您仍然需要对范围进行分组。

要返回所有范围，无论它们是否缺失，您都可以连接到具有范围的子查询。

SELECT Ranges.`range`, COALESCE(AVG(Q.`value`), 0) as `avg`
FROM
(
  SELECT 0 as `class`, ' 0-21' as `range`
  UNION ALL SELECT 21, '21-34'
  UNION ALL SELECT 34, '34-64'
  UNION ALL SELECT 64, '64+'
) Ranges
LEFT JOIN
(
  SELECT 
   `value`,
   case
   when `value` between  0 and 21 then 0
   when `value` between 21 and 34 then 21
   when `value` between 34 and 64 then 34
   when `value` > 64 then 64
   end as rangeclass
  FROM test
) Q ON Q.rangeclass = Ranges.`class`
GROUP BY Ranges.`class`, Ranges.`range`
ORDER BY Ranges.`class`

db <>提琴here

MySQL如何将平均值取到特定范围内

3 个答案: