-- 查詢男生、女生人數

-- 1. 條件查詢

SELECT case when Ssex='男' then '男生人數' ELSE '女生人數' END  '男女情況',count(1) '人數'  
 FROM student
 GROUP BY
case when Ssex='男' then '男生人數' ELSE '女生人數' END

 

 

 --2 . 單項依次查詢

SELECT count(Ssex) as 男生人數 FROM student WHERE Ssex='男';
SELECT count(Ssex) as 女生人數 FROM student WHERE Ssex='女';

 

 

 

 3.方法三

select 
sum(case when Ssex = '男' then 1 else 0 end) 男生人數,
sum(case when Ssex = '女' then 1 else 0 end) 女生人數 
from student