Question

所以我有这张桌子

             `gender  country  age  name  ID
              male    VietNam  20   Q     890 
              female  China    30   K     209
              female  Japan    25   O     302
              female  VietNam  20   L     203
              male    China    20   E     504`

我想提出一个查询，可以列出具有相同性别，同一国家和相同年龄的人数，按计数和分组来计算

Select gender,COUNT(*) from Employee Group BY gender Select country,COUNT(*) from Employee Group BY country Select age,COUNT(*) from Employee Group BY age

有没有办法只用一个选择？提前谢谢，抱歉我的英文不好

Answer 1

你可以通过UNION将这些结果放在结果集的单独记录中：

 Select 'Gender' as GroupByType, gender as GroupByValue ,COUNT(*) from Employee Group BY gender
 UNION ALL
 Select 'Country', country,COUNT(*) from Employee Group BY country
 UNION ALL
 Select 'Age', age,COUNT(*) from Employee Group BY age

Answer 2

如果你的RDBMS支持它...... SQL Server，Oracle和其他人做....不确定你在用什么。

Group by Grouping sets

Select count(*), gender, country, age 
from employee 
group by grouping sets ((gender), (country), (age ))

并且根据您要查找的输出类型...这将导致4列计数，性别，国家/地区和年龄列，其中4列中的2列始终为空。

除了没有groupbyType之外，它会产生类似于JNevill的输出，而不是group by

中的每个值都有一个单独的列

我们如何在SQL中同时使用多个计数和多个组？

2 个答案: