MySQL查询问题求助

Question

像segmentfault这样,
一个提问表,question,reply(当然可能不是这样设计的)

question

• id

• title

• user

• time

• ……

reply

• id

• q_id //问题ID

• user

• time

• ……

怎么一次查询出 问题title,时间,回答次数?

又例如学生表,成绩表
如何一次查询出每个学生有多少条成绩?

student

• id

• user

• pwd

• ……

grade

• id

• user

• score

• term

• ……

Answer 1

select users.user,users.name,(select count(*) from grade where users.user=grade.user) 
as total from users;

指定班级:

select users.user,users.name,(select count(*) from grade where users.user=grade.user) 
as total
from users where user like '2012%';

Answer 2

SELECT question.title, question.time,
(SELECT COUNT(*) FROM reply WHERE reply.q_id = question.id) AS reply_sum
FROM question

下面的问题类似