求sql语句（急）

[hiliye]

现有三个表，结构如下：读者reader(userid,u_name) 图书book(bookid,b_name) 借阅记录lend(record_id,userid,bookid) 主键分别为userid，bookid，record_id，要搜出 借书最多的五位读者的姓名和借阅册数。请指点！谢谢！

[vivianfdlpw]

select top 5
B.u_name
,count(1) as '借阅册数'

from lend A
join reader B on A.userid=B.userid
join book C on B.bookid=C.bookid
group by B.userid,B.u_name
order by count(1) desc

[hiliye]

第六行有错，应该是join book C on A.bookid=C.bookid，想必是笔误啦。请问count（1）与count（*）什么区别？