SQL Server Fuzzy Search с процент на съвпадение

Най-доброто, което успях да направя, е да опростя част от заявката и да я променя на функция с таблица. Скаларните функции са известни с лошо представяне и предимството на вградения TVF е, че дефиницията на заявката се разширява в основната заявка, подобно на изглед.

Това намалява значително времето за изпълнение на тестовете, които направих.

ALTER FUNCTION dbo.FuzySearchTVF (@Reference VARCHAR(200), @Target VARCHAR(200))
RETURNS TABLE
AS
RETURN
(   WITH N (n) AS 
    (   SELECT  TOP (ISNULL(CASE WHEN DATALENGTH(@Reference) > DATALENGTH(@Target) 
                                    THEN DATALENGTH(@Reference) 
                                ELSE DATALENGTH(@Target) 
                            END, 0))    
                ROW_NUMBER() OVER(ORDER BY n1.n)
        FROM    (VALUES (1), (1), (1), (1), (1), (1), (1), (1), (1), (1)) AS N1 (n)
        CROSS JOIN (VALUES (1), (1), (1), (1), (1), (1), (1), (1), (1), (1)) AS N2 (n)
        CROSS JOIN (VALUES (1), (1)) AS N3 (n)
        WHERE   @Reference IS NOT NULL AND @Target IS NOT NULL
    ), Src AS
    (   SELECT  Reference = CASE WHEN DATALENGTH(@Reference) > DATALENGTH(@Target) THEN @Reference
                                ELSE @Reference + REPLICATE('_', DATALENGTH(@Target) - DATALENGTH(@Reference))
                            END,
                Target = CASE WHEN DATALENGTH(@Target) > DATALENGTH(@Reference) THEN @Target
                                ELSE @Target + REPLICATE('_', DATALENGTH(@Target) - DATALENGTH(@Reference))
                            END,
                WordLength = CASE WHEN DATALENGTH(@Reference) > DATALENGTH(@Target) THEN DATALENGTH(@Reference) ELSE DATALENGTH(@Target) END
        WHERE   @Reference IS NOT NULL 
        AND     @Target IS NOT NULL
        AND     @Reference != @Target
    ), Scores AS
    (   SELECT  seq = t1.n ,
                Letter = SUBSTRING(s.Reference, t1.n, 1),
                s.WordLength ,
                LetterScore = s.WordLength - ISNULL(MIN(ABS(t1.n - t2.n)), s.WordLength)
        FROM    Src AS s
                CROSS JOIN N AS t1
                INNER JOIN N AS t2
                    ON SUBSTRING(@Target, t2.n, 1) = SUBSTRING(s.Reference, t1.n, 1)
        WHERE   @Reference IS NOT NULL 
        AND     @Target IS NOT NULL
        AND     @Reference != @Target
        GROUP BY t1.n, SUBSTRING(s.Reference, t1.n, 1), s.WordLength
    )
    SELECT  [Score] = 100 
    WHERE   @Reference = @Target
    UNION ALL
    SELECT  0
    WHERE   @Reference IS NULL OR @Target IS NULL
    UNION ALL
    SELECT  CAST(SUM(LetterScore) * 100.0 / MAX(WordLength * WordLength) AS NUMERIC(5, 2))
    FROM    Scores
    WHERE   @Reference IS NOT NULL 
    AND     @Target IS NOT NULL
    AND     @Reference != @Target
    GROUP BY WordLength
);

И това ще се нарича:

SELECT  f.Score
FROM    dbo.Customer AS c
        CROSS APPLY [dbo].[FuzySearch]('First Name Middle Name Last Name', c.FirstName) AS f

Все пак това е доста сложна функция и, в зависимост от броя на записите във вашата таблица с клиенти, мисля, че намаляването й до 1 секунда ще бъде малко предизвикателство.