The following will handle more levels than you can shake a stick at with numbers as large as 99999999. You'll need the DelimitedSplit8K function for this and I've included a link to that article after the code below.

--===== Build the test data

DECLARE @Result TABLE (Serial nvarchar(10),Title varchar(20))

INSERT INTO @Result

SELECT '1.1','a' UNION ALL

SELECT '1.2.1','b' UNION ALL

SELECT '1.2.2','C' UNION ALL

SELECT '1.2.3','G' UNION ALL

SELECT '1.11','B' UNION ALL

SELECT '2.3','B' UNION ALL

SELECT '2.11','B' UNION ALL

SELECT '2.2','C' UNION ALL

SELECT '1.5','E' UNION ALL

SELECT '1.3','E'

;

--===== Solve the problem by creating a hierarchical sort path using a very high speed

-- method for the right alignment of integer data (thanks, Dwaine)

WITH

cteBuildPath AS

(

SELECT r.Serial

,r.Title

,SortPath =

(--==== Split the parts of each Serial and reassemble as a hierarchical path

SELECT RIGHT(split.Item+100000000,8) --Converts each # to a zero filled right aligned number of 8 digits.

FROM @Result r1

CROSS APPLY dbo.DelimitedSplit8K(Serial,'.') split

WHERE r1.Serial = r.Serial

FOR XML PATH('')

)

FROM @Result r

)

SELECT Serial,Title

FROM cteBuildPath

ORDER BY SortPath

;

The DelimitedSplit8K function may be found at the following URL...

http://www.sqlservercentral.com/articles/Tally+Table/72993/