SQL怎么判断两个时间段是否有交叉？

sql 代码：

if  exists (select * from sys.objects where object_id = object_id(n'[dbo].[fun_gettimeslotdays]'))
drop function [dbo].fun_gettimeslotdays
go

-- =============================================
-- author:        
-- create date: <2012-07-18>
-- description:    <判断两个时间断是否有交叉,如果有则返回1,否则返回0>
-- =============================================
create function dbo.fun_gettimeslotdays(
@fromdate datetime,
@todate datetime,
@startdate datetime,
@enddate datetime
)
returns int 
as 
begin
   declare @ret int;
   if(datediff(day,@fromdate,@enddate)>=0 and datediff(day,@enddate,@todate)>=0 )
      set @ret=1;
   if(datediff(day,@startdate,@todate)>=0 and datediff(day,@todate,@enddate)>=0 )
      set @ret=1;
   if (@ret is null)
      set @ret=0;
   return @ret;
end
go

测试代码：

select dbo.fun_gettimeslotdays('2012-03-01','2012-03-10','2012-02-10','2012-02-20');
select dbo.fun_gettimeslotdays('2012-03-01','2012-03-10','2012-02-01','2012-03-01');
select dbo.fun_gettimeslotdays('2012-03-01','2012-03-10','2012-03-01','2012-03-02');
select dbo.fun_gettimeslotdays('2012-03-01','2012-03-10','2012-03-10','2012-03-11');
select dbo.fun_gettimeslotdays('2012-03-01','2012-03-10','2012-03-11','2012-03-11');