• 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 '1.2.3.4','G' UNION ALL

    SELECT '1.11','B' UNION ALL

    SELECT '1.2.33.4.5','Extra row' 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'

    SELECT r.*

    FROM @Result r

    CROSS APPLY (SELECT n = CHARINDEX('.',Serial,0)) p1

    CROSS APPLY (SELECT n = NULLIF(CHARINDEX('.',Serial,p1.n+1),0)) p2

    CROSS APPLY (SELECT n = NULLIF(CHARINDEX('.',Serial,p2.n+1),0)) p3

    CROSS APPLY (SELECT n = NULLIF(CHARINDEX('.',Serial,p3.n+1),0)) p4

    CROSS APPLY (

    SELECT

    Elem1 = LEFT(Serial, p1.n-1),

    Elem2 = SUBSTRING(Serial, p1.n+1, ISNULL(p2.n-(p1.n+1),8000)),

    Elem3 = SUBSTRING(Serial, p2.n+1, ISNULL(p3.n-(p2.n+1),8000)),

    Elem4 = SUBSTRING(Serial, p3.n+1, ISNULL(p4.n-(p3.n+1),8000)),

    Elem5 = SUBSTRING(Serial, p4.n+1, 8000)

    ) x

    ORDER BY CAST(x.Elem1 AS INT), CAST(x.Elem2 AS INT), CAST(x.Elem3 AS INT), CAST(x.Elem4 AS INT), CAST(x.Elem5 AS INT)

    “Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw

    For fast, accurate and documented assistance in answering your questions, please read this article.
    Understanding and using APPLY, (I) and (II) Paul White
    Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden