请教一条SQL语句(如何从表A得到表B)？
表A:   from       to
          100         200
          200         300
          300         400
          500         550
          550         600
          600         650
          650         700
表B:   from       to
          100         400
          500         700

------解决方案--------------------
Create Table A
([from] Int,
[to] Int)
Insert A Select 100, 200
Union All Select 200, 300
Union All Select 300, 400
Union All Select 500, 550
Union All Select 550, 600
Union All Select 600, 650
Union All Select 650, 700
GO
Select
A.[from],
Min(B.[to]) As [to]
From
(Select [from] From A T Where Not Exists (Select [to] From A Where [to] = T.[from])) A
Inner Join
(Select [to] From A T Where Not Exists (Select [from] From A Where [from] = T.[to])) B
On A.[from] <= B.[to]
Group By A.[from]
GO
Drop Table A
--Resutl
/*
from to
100 400
500 700
*/
------解决方案--------------------
Create Table A
([from] Int,
[to] Int)
Insert A Select 100, 200
Union All Select 200, 300
Union All Select 300, 400
Union All Select 500, 550
Union All Select 550, 600
Union All Select 600, 650
Union All Select 650, 700
GO

select ta.[from],[to]=min(tb.[to])
from A as ta , A as tb
where ta.[from] <= tb.[to]
and not exists(Select [to] From A Where [to] = Ta.[from])
and Not Exists (Select [from] From A Where [from] = Tb.[to])
group by ta.[from]