Overlapping Sets

I have the following table structure

CREATE TABLE [dbo].[QDisc](
[Id] [int] NOT NULL,
[MinVal] [int] NOT NULL,
[MaxVal] [int] NOT NULL,
[PerVal] [int] NOT NULL,
CONSTRAINT [PK_QDisc] PRIMARY KEY CLUSTERED
(
[Id] ASC
)WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]

I need to be able to select unique overlapping sets of data based on the minval and maxval.

Simple Example
minval maxval
5 15
16 25
10 20

query would produce
minval maxval
5 10
11 15
16 20
21 25

More Complex example
minval maxval
5 15
16 25
10 20
7 7
1 100

query would produce
minval maxval
1 5
6 6
7 7
8 10
11 15
16 20
21 25
26 100

Extra points if anyone can do this without SP and cursor but I'd be satisfied if someone supplied it that way.Extra points for doing your homework assignment for you?|||Extra points if anyone can do this without SP and cursor but I'd be satisfied if someone supplied it that way.Gosh - generous and gracious. How super.|||I'll give myself extra credit

ALTER PROCEDURE [dbo].[usp_Select_Disc]
AS
BEGIN
-- SET NOCOUNT ON added to prevent extra result sets from
-- interfering with SELECT statements.
SET NOCOUNT ON;

select minval, maxval into #QtyRange from qdisc

declare @.minval int
declare @.maxval int
declare @.xminval int
declare @.xmaxval int

declare @.pmaxval int
declare @.pmaxva2 int

declare @.loopflg bit
set @.loopflg = 1
while @.loopflg = 1
begin
set @.loopflg = 0
DECLARE curSel CURSOR FOR select minval, maxval from #QtyRange order by minval
open curSel
fetch next from curSel into @.minval, @.maxval
WHILE (@.@.FETCH_STATUS <> -1)
begin

set @.xminval = null
set @.xmaxval = null

select top(1) @.xminval = minval, @.xmaxval = maxval from #QtyRange where minval > @.minval or maxval > @.maxval order by minval

if @.maxval > @.xminval
begin
set @.pmaxval = @.maxval
if @.minval = @.xminval
begin
set @.pmaxva2 = @.xmaxval
update #QtyRange set maxval = @.xminval where minval = @.minval and maxval = @.maxval
update #QtyRange set minval = @.xminval + 1, maxval = @.pmaxval where minval = @.xminval and maxval = @.xmaxval
insert into #QtyRange values (@.pmaxval + 1, @.pmaxva2)
set @.loopflg = 1
break
end
update #QtyRange set maxval = @.xminval - 1 where minval = @.minval and maxval = @.maxval

if @.xmaxval > @.pmaxval
begin
set @.pmaxva2 = @.xmaxval
update #QtyRange set maxval = @.pmaxval where minval = @.xminval and maxval = @.xmaxval
insert into #QtyRange values (@.pmaxval + 1, @.pmaxva2)
set @.loopflg = 1
break
end
if @.xmaxval < @.pmaxval
insert into #QtyRange values (@.xmaxval + 1, @.pmaxval)
set @.loopflg = 1
end

if @.maxval = @.xminval
begin
set @.pmaxval = @.maxval

if @.minval = @.maxval
begin
update #QtyRange set minval = @.pmaxval + 1 where minval = @.xminval and maxval = @.xmaxval
set @.loopflg = 1
break
end
else
begin
update #QtyRange set maxval = @.pmaxval - 1 where minval = @.minval and maxval = @.maxval
if @.xminval <> @.xmaxval
begin
insert into #QtyRange values (@.pmaxval, @.pmaxval)
update #QtyRange set minval = @.pmaxval + 1 where minval = @.xminval and maxval = @.xmaxval
set @.loopflg = 1
break
end
end
end
fetch next from curSel into @.minval, @.maxval
end
Close curSel
DEALLOCATE curSel
end

select distinct(a.minval), a.maxval, sum(qdisc.perval) from #QtyRange a
inner join qdisc on a.minval >= qdisc.minval and a.maxval <= qdisc.maxval
group by a.minval,a.maxval
order by minval
END|||I'll give myself extra credit

You shouldn't, you used a cursor.|||You shouldn't, you used a cursor.
I'm not sure it can be done without a cursor or some other form of looping. I see no way to do it with a simple SELECT statement.|||neither do I, but that was his self-professed requirement for extra points.|||No no no. That was the requirement for YOU to get extra points. He, of course, is free to give himself as much credit as he wants.|||how many points do i need to get a free ship?|||this worked for both the data sets provided by u. i have tried with a couple of other sets and appears to be working. interested to know if it worked at your end or not...

create table #tt1 (Id int identity (1,1), Val int )
insert into #tt1 (Val) select Val from (
select Minval as Val from QDisc
union all
select Maxval as Val from QDisc
) A order by 1

select B.Id,A.Val AVal, B.Val BVal, C.Val CVal into #tt2
from #tt1 A, #tt1 B, #tt1 C where A.Id+1 =* B.Id and C.Id-1 =* B.Id

update #tt2 set BVal=BVal-1 where AVal+1=BVal
update #tt2 set CVal=Null where BVal+1=CVal
update #tt2 set CVal=CVal-1 from #tt2 A where A.CVal= (select BVal from #tt2 where #tt2.id = A.id+1 and BVal=CVal)

select
BVal+ case when BVal=(select min(BVal) from #tt2) then 0 when BVal= CVal then 0 else 1 end as MinVal,
CVal as MaxVal
from #tt2
where CVal is not null