求一条统计的sql语句

Question

id userip          pv  addtime            username10 116.24.181.55 2 2011/11/10 17:41:45  guest
11 116.24.181.55 1 2011/11/10 17:45:56   guest
12 116.24.181.63 1 2011/11/10 17:46:45  lintao
13 116.24.181.63 2 2011/11/10 17:47:11  lintao
14 116.24.181.65 1 2011/11/10 17:47:49   guest
15 116.24.181.65 2 2011/11/11 20:29:52   guest
16 116.24.181.65 1 2011/11/11 22:57:02  guest1
17 116.24.181.65 1 2011/11/11 23:30:30  guest1
18 116.24.181.65 1 2011/11/12 23:30:48   guest2
19 116.24.181.65 2 2011/11/12 23:31:02   guest2
20 116.24.181.65 1 2011/11/13 17:14:57   guest3
21 116.24.181.65 1 2011/11/13 17:14:59   guest3想在以上数据里统计出一个类似UV值的一天内唯一数量。即：同一天内 + 同一IP + 同一用户名 = UV，如上数据统计结果应为7条。谢谢

Answer 1

select ip,date(addtime),username,count(*)
from tb
group by ip,date(addtime),username

Answer 2

select distinct (userip ,date(addtime ),username)
from table1

Answer 3

出错，distinct好像不能放个多字段吧

Answer 4

select count(distinct userip ,date(addtime ),username)
from table1