SQL Server 多条查询结果组合

假如存在下面这张表users：

1.通过sql语句返回总人数、男生总数和女生总数

select count(1) '总人数',
(select count(1) from users u2 where u2.sex=1) '男生总数',
(select count(2) from users u3 where u3.sex=0) '女生总数'
 from users u1;

2.按照班级统计总人数，总男生人数和女生人数

select u0.class,count(1) '总人数',
(select count(1) from users u1 where  u1.sex=1 and u1.class=u0.class) '男生总数',
(select count(1) from users u2 where  u2.sex=0 and u2.class=u0.class) '女生总数'
from users u0 group by u0.class;