Question

我试图计算出我的数据中男性占多大比例，女性占多大比例。

我有以下代码：

select 
  SUM(CASE WHEN Gender = 'M' THEN 1 ELSE 0 END) / COUNT(Gender) as perc_male,
  SUM(CASE WHEN Gender = 'F' THEN 1 ELSE 0 END) / COUNT (Gender) as perc_female
From [my_table]

但是运行此命令时，我得到0％。有人可以看到我在这里做错什么吗？

谢谢

Answer 1

我认为值小于1，这就是为什么您得到0 尝试如下

select 
SUM(CASE WHEN Gender = 'M' THEN 1 ELSE 0 END) / COUNT(Gender)*1.00
 as perc_male,
SUM(CASE WHEN Gender = 'F' THEN 1 ELSE 0 END) / COUNT (Gender)*1.00 
as perc_female
From [my_table]

或在float数据类型中使用显式强制转换

Answer 2

只需使用：

select 
SUM(CASE WHEN Gender = 'M' THEN 1.0 ELSE 0.0 END) / COUNT(Gender)
as perc_male,
SUM(CASE WHEN Gender = 'F' THEN 1.0 ELSE 0.0 END) / COUNT (Gender) 
as perc_female
From [my_table]

您正在使用整数。在处理整数时，SQL总是尝试返回整数，在这种情况下-ot向下舍入为0。

Answer 3

使用其中一个值的显式转换来获得所需的精度，例如

select 
  SUM(CASE WHEN Gender = 'M' THEN 1 ELSE 0 END) / cast(COUNT(Gender) as decimal(5,3)) as perc_male,
  SUM(CASE WHEN Gender = 'F' THEN 1 ELSE 0 END) / cast(COUNT(Gender) as decimal(5,3)) as perc_female
From [my_table]

Answer 4

问题是整数除法。我认为最简单的方法是使用AVG()：

SELECT AVG(CASE WHEN Gender = 'M' THEN 1.0 ELSE 0 END) as perc_male,
       AVG(CASE WHEN Gender = 'F' THEN 1.0 ELSE 0 END) as perc_female
FROM [my_table]

从char值计算％

4 个答案: