查询新增人员数量
做统计的，查询每天的新增的人员
表结构
userid datetime
1 2014-01-13
2 2014-01-13
3 2014-01-13
1 2014-01-14
4 2014-01-14

结果
2014-01-13 为三个人
2014-01-14 为一个

2014-01-14 编号为1的在13号登录过所以不是新增的。4在14之前没有登录过所以是新增的
一句话，每天的登录记录中，之前没有登录过的算是新增的
[解决办法]

create table test(userid int, datetime datetime)
 
insert into test
select 1       ,'2014-01-13' union all
select 2       ,'2014-01-13' union all
select 3       ,'2014-01-13' union all
select 1       ,'2014-01-14' union all
select 4       ,'2014-01-14'
go


IF object_id('tempdb..#t','U')IS NOT NULL 
DROP TABLE #t
select *,
       (select COUNT(*) from test t2 
        where t1.userid = t2.userid and t1.datetime>=t2.datetime) rownum INTO #t
from test t1
 
select datetime,COUNT(*) '人数',(SELECT COUNT(1) FROM #t b WHERE a.datetime=b.datetime)[总人数]
from #t a
where rownum = 1
group by datetime
/*
datetime                人数          总人数
----------------------- ----------- -----------
2014-01-13 00:00:00.000 3           3
2014-01-14 00:00:00.000 1           2

*/

--drop table test

create table test(userid int, datetime datetime)

insert into test
select 1       ,'2014-01-13' union all
select 2       ,'2014-01-13' union all
select 3       ,'2014-01-13' union all
select 1       ,'2014-01-14' union all
select 4       ,'2014-01-14'
go

select datetime,COUNT(*) '人数',
       (select COUNT(*) from test t2 where t2.datetime = t.datetime) as  总人数
from 
(
select *,
       (select COUNT(*) from test t2 
        where t1.userid = t2.userid and t1.datetime>=t2.datetime) rownum
from test t1
)t
where rownum = 1
group by datetime
/*
datetime人数总人数
2014-01-13 00:00:00.00033
2014-01-14 00:00:00.00012
*/