计算男性,女性和总数

Question

我想计算学生表中指定特定年份的男,女,全学生数.我希望结果可以显示在表格中:

====================================
| Label    |  Value   |   Year     |
====================================
| Male     |   0      |   2013     |
| Female   |  23      |   2013     |
| Total    |  23      |   2013     |
====================================

如果指定年份没有男性/女性匹配,则查询应显示0.知道如何才能实现这一目标吗？

提前致谢

Answer 1

考虑以下查询:

select
  max(registeredYear) as year,
  count(case when gender='Male' then 1 end) as male_cnt,
  count(case when gender='Female' then 1 end) as female_cnt,
  count(*) as total_cnt
from student
where registeredYear = 2013
group by registeredYear;

结果将是这样的:

Year male_cnt female_cnt total_cnt
---- -------- ---------- ---------
2013        0         23        23

您可以将此结果转换为所需的表单.如果你想在查询中这样做,那么你可以这样做:

with t as (
    select
      max(registeredYear) as year,
      count(case when gender='Male' then 1 end) as male_cnt,
      count(case when gender='Female' then 1 end) as female_cnt,
      count(*) as total_cnt
    from student
    where registeredYear = 2013
    group by registeredYear)
select 'Male', male_cnt as male, year from t
union all
select 'Female', female_cnt as male, year from t
union all
select 'Total', total_cnt as male, year from t
;

Answer 2

你应该使用:

select name, COUNT(*)as tot, 
  COUNT(case when details.gender='male' then 1 end) as male,
  COUNT(case when details.gender='female' then 1 end) as female 
  from details  group by name