oracle经典sql面试

  一个学校表，school,列class 班级，name  学生姓名，sex 性别，男为'M'，女为'F',一个学校表很多的班级，查询出男生，女生数量相同的班级。

好久不搞sql,几乎都忘光了，特此纪念，

select tem.class from(  
select class,  
       (select count(sex)  
          from schools s1  
         where s1.class = s.class  
           and s1.sex = 'M') AS MCOUNT,  
       (select count(sex)  
          from schools s1  
         where s1.class = s.class  
           and s1.sex = 'F') AS FCOUNT  
  from schools s  
group by class  
) tem where tem.MCOUNT = tem.FCOUNT