Sql server 2008 如何从SQL server的两个不同表列中获取一个不同的ListofDate列

有两个表页，包含数据

我需要显示这两个表中不同的ListofDates和employeeid，这两个表的Date列都有一些条件，即在Leave表approvalstatus='Approved'和startdate/enddate期间持续时间中

表架构：

期望输出：

Empid ListofDate
1     2013-04-22 00:00:00.000
1     2013-04-19 00:00:00.000
1     2013-04-15 00:00:00.000
2     2013-04-21 00:00:00.000
3     2013-04-26 00:00:00.000
3     2013-04-02 00:00:00.000

目前我正在尝试：

select ListOfDates
from 
(
 select leavedate as ListOfDates from leaves where approvalstatus='Approved' and leavedate >='20130302' and  leavedate <'20130501'
 union
 select absentdate  as ListOfDates from Attendanceatd where  absentdate >='20130302' and  absentdate <'20130501'
)t1
group by ListOfDates 

---

无法将employeeId与日期列表一起获取我认为您不需要分组。这就是你想要的

 select idemp_lv, leavedate as ListOfDates
 from leaves
 where approvalstatus='Approved' and leavedate >='20130302' and  leavedate <'20130501'
 union
 select idemp_at, absentdate  as ListOfDates
 from Attendanceatd
 where  absentdate >='20130302' and  absentdate <'20130501'

如果使用UNION ALL，则会自动记录差异

---

除非我遗漏了什么，否则我应该做这件事。只需记住，联合会更快，但会产生更具指令性的sql排序。始终查看执行计划以检查性能。

感谢您的promp回复，是的，这很好，实际上我正在与group By进行斗争。就我所知，您能告诉我哪一个使用UNION或UNION ALL的性能更好吗？因为Andrew Jansen的答案也很好。Andrew的答案需要更多的处理。我的组员一步就组成了工会。

select EmpId,ListOfDates
from 
(
select idemp_lv as EmpId ,leavedate as ListOfDates from leaves where approvalstatus='Approved' 
union all
select idemp_at as EmpId , absentdate  as ListOfDates from Attendanceatd
)T1
where ListOfDates between '2013-03-02' and '2013-05-01'
group by  EmpId,ListOfDates

select distinct empid, ListOfDates
from 
(
 select idemp_lv as empid, leavedate as ListOfDates from leaves where approvalstatus='Approved' and leavedate >='20130302' and  leavedate <'20130501'
 union all
 select idemp_at as empid, absentdate  as ListOfDates from Attendanceatd where  absentdate >='20130302' and  absentdate <'20130501'
)t1
group by empid, ListOfDates 

select EmpId,ListOfDates
from 
(
select idemp_lv as EmpId ,leavedate as ListOfDates from leaves where approvalstatus='Approved' 
union all
select idemp_at as EmpId , absentdate  as ListOfDates from Attendanceatd
)T1
where ListOfDates between '2013-03-02' and '2013-05-01'
group by  EmpId,ListOfDates