求写SQL文的大神帮我解决一下问题

[mty]

12.表结构如下：
表A： Employee_sn StartDate EndDate
1 '2007-01-02' '2007-01-03'
1 '2007-01-05' '2007-01-06'
1 '2007-01-09' '2007-01-13'
2 '2007-02-02' '2007-02-03'
3 '2007-04-02' '2007-04-03'

表B： Employee_sn CreateDate
1 '2007-01-02'
1 '2007-01-05'
1 '2007-01-03'
3 '2007-04-02'
1 '2007-01-04'
1 '2007-01-02'
2 '2007-02-02'

要得到的结果：
Employee_sn StartDate EndDate Count
1 '2007-01-02' '2007-01-03' 3
1 '2007-01-05' '2007-01-06' 1
1 '2007-01-09' '2007-01-13' 0
2 '2007-02-02' '2007-02-03' 1
3 '2007-04-02' '2007-04-03' 1


这个SQL文怎么写啊，从来都没写过这样的题啊。

[WWWWA]

select *,(select count(*) from b where a.Employee_sn=Employee_sn and CreateDate between a.StartDate and a.EndDate ) from a

[Rotel-刘志东]

select a.Employee_sn,a.startDate,a.EndDate,count(a.startDate)+count(b.createDate) as count from 表A a,表B b where a.Employee_sn=b.Employee_sn；

[Rotel-刘志东]

select a.Employee_sn,a.startDate,a.EndDate,count(a.startDate)+count(b.createDate) as count from 表A a,表B b where a.Employee_sn=b.Employee_sn group by a.Employee_sn,a.startDate,a.EndDate;