--最好是列出:M.Meeting_ID,M.Meeting_Name,Attendee1(第1天人数),Attendee2(第2天人数)...Attendee5(第5天人数) 
select M.Meeting_ID, M.Meeting_Name, Attendee1=count(A1.Meeting_ID), Attendee2=count(A2.Meeting_ID),
    Attendee3=count(A3.Meeting_ID), Attendee4=count(A4.Meeting_ID), Attendee5=count(A5.Meeting_ID) 
from Meeting M left join Attendee A1 on M.Meeting_ID=A1.Meeting_ID and M1.StartDate between A1.InDate and A1.OutDate
left join Attendee A2 on M.Meeting_ID=A2.Meeting_ID and dateadd(day,1,M1.StartDate) between A2.InDate and A2.OutDate
left join Attendee A3 on M.Meeting_ID=A3.Meeting_ID and dateadd(day,2,M1.StartDate) between A3.InDate and A3.OutDate
left join Attendee A4 on M.Meeting_ID=A4.Meeting_ID and dateadd(day,3,M1.StartDate) between A4.InDate and A4.OutDate
left join Attendee A5 on M.Meeting_ID=A5.Meeting_ID and dateadd(day,4,M1.StartDate) between A5.InDate and A5.OutDate
group by M.Meeting_ID, M.Meeting_Name

------解决方案--------------------
似乎忽悠了一个问题，入住/与会之间有联系，但不是必然联系。

与会但不入住，或反之，都有可能。

------解决方案--------------------

--每个会议第一天人数
select a.meeting_id,rtrim(b.name)+'1' meeting_name,count(*) as attendee  
from attendee a,metting b
where a.meeting_id=b.id and b.startdate between a.indate and a.outdate
group by a.metting_id,rtrim(b.name)+'1'

同理每个会议第2-5天的人数可依此推
如第2天,将+'1'改为+'2',将a.startdate加1

再将5个查询结果用union all加起来却可

------解决方案--------------------
每个 meeting 5天的情况：
select ID, Name,  
	(select Count(distinct ID)
	 from Attendee
	 where Meeting_ID = A.ID and Indate < A.StartDate  
		and OutDate > A.StartDate) as Attendee1,
	(select Count(distinct ID)
	 from Attendee
	 where Meeting_ID = A.ID and Indate < A.StartDate + 1  
		and OutDate > A.StartDate + 1) as Attendee2,
	(select Count(distinct ID)
	 from Attendee
	 where Meeting_ID = A.ID and Indate < A.StartDate + 2  
		and OutDate > A.StartDate + 2) as Attendee3,
	(select Count(distinct ID)
	 from Attendee
	 where Meeting_ID = A.ID and Indate < A.StartDate + 3  
		and OutDate > A.StartDate + 3) as Attendee4,
	(select Count(distinct ID)
	 from Attendee
	 where Meeting_ID = A.ID and Indate < A.StartDate + 4  
		and OutDate > A.StartDate + 4) as Attendee5
from Meeting

------解决方案--------------------
对任意天
创建一临时表，用while 语句
各天人数的查询语句用动态生成
　用insert into 临时表　exec(动态sql语句）
将结果插入到临时表中
再对临时表查询.


------解决方案--------------------
SQL code

--不知道这是不是你要的样式和结果
--创建表
CREATE TABLE MEETING(ID INT,NAME VARCHAR(20),STARTDATE VARCHAR(20),ENDDATE VARCHAR(20))
INSERT INTO MEETING
SELECT 1,'十六大','2007-10-01','2007-10-05'
UNION ALL SELECT 2,'十七大','2007-10-15','2007-10-20'

CREATE TABLE ATTENDEE(ID INT,NAME VARCHAR(2