有个sql统计语句不会写，求教
我有一个表，精简了说就是记录访问者IP以及访问时间，字段与数据如下——
表table1
ipaddress dt
192.168.1.2542013-03-05 15:41:17.047
220.181.89.2092013-03-05 15:44:23.713
65.55.52.892013-03-05 15:46:28.643
65.55.52.892013-03-05 15:46:31.200
220.181.89.2092013-03-05 15:49:34.533
我已经写了一句sql语句，用来统计当天有多少个访问量，如下——
select convert(varchar(10),dt,120) as a1,
count(ipaddress) as a2
from table1
group by convert(varchar(10),dt,120) order by a1 DESC
a2字段显示的是总数，可是我现在想增加一个字段a3，希望能显示每一天一共有多少个不同的ip地址，如我举例那5行数据，统计出的结果应该为——
a1 a2 a3
2013-03-05 5 3
请问这个带a3的语句怎么写？
sql group?by
[解决办法]
select convert(varchar(10),dt,120) as a1,
count(ipaddress) as a2,
count(distinct ipaddress) as a3
from table1
group by convert(varchar(10),dt,120) order by a1 DESC
