Question

我的数据想要这个

Name    Similar_Percentage      
A           15
B           20
C           65

我想要这样

Similar_Percentage          count(*)
Less than 20            2
Less than 70            1

如何为此编写查询。我知道这样做了，但它显示的是一个数据。

Answer 1

用例何时

  select case when Similar_Percentage<20  then 'Less than 20'
            when (Similar_Percentage<70)  then 'Less than 70' end as Percentage,count(*)
    from table group by case when Similar_Percentage<20 then 'Less than 20'
            when (Similar_Percentage<70) then 'Less than 70' end


with cte as (

select  15 as Similar_Percentage
union all
select 20
union all
select 65

)select case when Similar_Percentage<=20  then 'Less than 20'
            when (Similar_Percentage<70)  then 'Less than 70' end as Percentage,count(*)
    from cte group by case when Similar_Percentage<=20 then 'Less than 20'
            when (Similar_Percentage<70) then 'Less than 70' end

demo link

Percentage  count(*)
Less than 20    2
Less than 70    1

Answer 2

另一种方法可能如下。

SELECT 'Less than 20' Percentage, 
       Count(*)       [Count(*)] 
FROM   tablename 
WHERE  similar_percentage <= 20 
UNION ALL 
SELECT 'Less than 70' Percentage, 
       Count(*)       [Count(*)] 
FROM   tablename 
WHERE  similar_percentage <= 70 
       AND similar_percentage > 20

Answer 3

在派生表（子查询）中使用case 表达式（子查询）进行分类。 GROUP BY其结果：

select percentage, count(*)
from
(
    select case when Similar_Percentage <= 20 then 'Less than 20'
                when Similar_Percentage <= 70 then 'Less than 70'
                else 'More than 70'
           end as percentage
    from tablename
) dt
group by percentage

Answer 4

MySQL允许您在group by中使用列别名。这样可以简化查询。

我还建议使用显式的order by，以便按所需顺序获得结果：

select (case when Similar_Percentage <= 20  then 'Less than 20'
             when Similar_Percentage < 70 then 'Less than 70'
        end) as Percentage,
       count(*)
from cte
group by Percentage
order by min(Similar_Percentage)

MySQL获得计数百分比

4 个答案: