SQL UDF - Calculate Distance Between Strings (Levenshtein)

This is basically a sql vairant to calculate % of closeness of strings, Not same as Fuzzy Match in python, This incorporates levenshtein Logic

a. Main Logic

CREATE FUNCTION [dbo].[Levenshtein](@s1 NVARCHAR(MAX), @s2 NVARCHAR(MAX))
RETURNS INT
AS
BEGIN
    DECLARE @lenS1 INT = LEN(@s1),
            @lenS2 INT = LEN(@s2),
            @i INT,
            @j INT,
            @cost INT;

    -- Table variable to store distances
    DECLARE @d TABLE (i INT, j INT, cost INT);

    -- Initialize distances
    -- Fill for @i (vertical)
    SET @i = 0;
    WHILE @i <= @lenS1
    BEGIN
        INSERT INTO @d (i, j, cost) VALUES (@i, 0, @i);
        SET @i = @i + 1;
    END

    -- Fill for @j (horizontal)
    SET @j = 0;
    WHILE @j <= @lenS2
    BEGIN
        INSERT INTO @d (i, j, cost) VALUES (0, @j, @j);
        SET @j = @j + 1;
    END

    -- Fill matrix for distances
    SET @i = 1;
    WHILE @i <= @lenS1
    BEGIN
        SET @j = 1;
        WHILE @j <= @lenS2
        BEGIN
            SET @cost = CASE 
                           WHEN SUBSTRING(@s1, @i, 1) = SUBSTRING(@s2, @j, 1) THEN 0
                           ELSE 1
                        END;

            DECLARE @cost1 INT, @cost2 INT, @cost3 INT;
            
            -- Retrieve costs for comparison
            SELECT @cost1 = cost FROM @d WHERE i = @i - 1 AND j = @j;   -- Deletion
            SELECT @cost2 = cost FROM @d WHERE i = @i AND j = @j - 1;   -- Insertion
            SELECT @cost3 = cost FROM @d WHERE i = @i - 1 AND j = @j - 1; -- Substitution

            -- Calculate the minimum of the three values and insert into table
            INSERT INTO @d (i, j, cost)
            VALUES (@i, @j, 
                    (SELECT MIN(val) 
                     FROM (VALUES (@cost1 + 1), (@cost2 + 1), (@cost3 + @cost)) AS value(val))
                   );

            SET @j = @j + 1;
        END
        SET @i = @i + 1;
    END

    -- Return final distance (bottom-right corner of the matrix)
    RETURN (SELECT cost FROM @d WHERE i = @lenS1 AND j = @lenS2);
END;
GO

b. % Calculation

CREATE FUNCTION [dbo].[Levenshtein_Percentage] (@str1 NVARCHAR(MAX), @str2 NVARCHAR(MAX))
RETURNS DECIMAL(10,2)
as
begin
RETURN (
SELECT 
    (1.0 - CAST(dbo.Levenshtein(@str1, @str2) AS FLOAT) / CAST(GREATEST(LEN(@str1), LEN(@str2)) AS FLOAT)) * 100 AS SimilarityPercentage)
END;
GO

Usage:

select [dbo].[Levenshtein_Percentage]('hello','dubmo')
20.00

select [dbo].[Levenshtein_Percentage]('hello','zyx')
0.00

select [dbo].[Levenshtein_Percentage]('hello','hello dear')
50.00

select [dbo].[Levenshtein_Percentage]('hello','hellox')
83.33

select [dbo].[Levenshtein_Percentage]('hello','HELLo')
100.00