SQL SERVER number segment Merging

Code: create table # TMP (
Id int,
S nvarchar (100 ),
E nvarchar (100 ))
 
Insert into # TMP (ID, S, E)
SELECT 2000, UNION ALL
SELECT 4000, UNION ALL
SELECT 6000, UNION ALL
SELECT 30000, UNION ALL
SELECT 50000, UNION ALL
SELECT 40000

SELECT max (a. id) id, a. s, min (case when (B. e is not null) THEN B. e ELSE a. e end) FROM # tmp
Left JOIN # tmp B ON a. id = B. id AND a. e + 1 = B. s
Where not exists (SELECT 1 FROM # tmp WHERE e + 1 = a. s AND id = a. id)
And not exists (SELECT 1 FROM # tmp WHERE s + 1 = B. e AND id = a. id)
Group by a. id, a. s order by id

Result <p> id s e
1 4000
1 5000 6000
2 20001 40000 </p> <p> (3 rows affected)
</P>

Url: http://greatverve.cnblogs.com/archive/2011/07/22/sql-Merge.html