sql server 2008语言基础: 集合

--declare @t table(n int)
--insert into @t values(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)
--select * from @t 

--返回在2008年1月有订单活动, 而在08年2月没有订单活动的客户和雇员.
--select custid, empid from Sales.Orders where orderdate>='2008-01-01' and orderdate<'2008-02-01'
--except
--select custid, empid from Sales.Orders where orderdate>='2008-02-01' and orderdate<'2008-03-01'

--返回在08年1月和2月都有订单活动的客户和雇员
--select custid, empid from Sales.Orders where orderdate>='2008-01-01' and orderdate<'2008-02-01'
--intersect
--select custid, empid from Sales.Orders where orderdate>='2008-02-01' and orderdate<'2008-03-01'

--在08年1月和2月有, 在07年没有的客户和雇员
--(select custid, empid from Sales.Orders where orderdate>='2008-01-01' and orderdate<'2008-02-01'
--intersect
--select custid, empid from Sales.Orders where orderdate>='2008-02-01' and orderdate<'2008-03-01'
--)
--except
--select custid, empid from Sales.Orders where orderdate>='2007-1-01' and orderdate<'2008-01-01'

select country,region,city from hr.Employees
union all
select country,region,city from Production.Suppliers