在處理SQL的哈羅溫克勒距離算法

Question

我一直在琢磨如何實現這個算法在處理SQL個月的實施，https://en.wikipedia.org/wiki/Jaro%E2%80%93Winkler_distance

如何能不能做到？

Answer 1

今天我終於偶然發現了this堆棧溢出 - leebickmtu顯示了C＃中的一個實現，最初是從Java移植過來的。我冒昧地將其移植到Transact SQL函數中，盡情享受吧！

IF OBJECT_ID (N'dbo.InlineMax', N'FN') IS NOT NULL 
    DROP FUNCTION dbo.InlineMax; 
GO 

CREATE FUNCTION dbo.InlineMax(@valueOne int, @valueTwo int) 
    RETURNS FLOAT 
AS 
BEGIN 
    IF @valueOne > @valueTwo 
    BEGIN 
     RETURN @valueOne 
    END 

    RETURN ISNULL(@valueTwo, @valueOne) 
END; 
GO 

IF OBJECT_ID (N'dbo.InlineMin', N'FN') IS NOT NULL 
    DROP FUNCTION dbo.InlineMin; 
GO 

CREATE FUNCTION dbo.InlineMin(@valueOne int, @valueTwo int) 
    RETURNS FLOAT 
AS 
BEGIN 
    IF @valueOne < @valueTwo 
     RETURN @valueOne 

    RETURN @valueTwo 
END; 
GO 

IF OBJECT_ID (N'dbo.JaroWinklerDistance', N'FN') IS NOT NULL 
    DROP FUNCTION dbo.JaroWinklerDistance; 
GO 

CREATE FUNCTION dbo.JaroWinklerDistance(@stringOne varchar(MAX), @stringTwo varchar(MAX)) 
RETURNS FLOAT 
WITH EXECUTE AS CALLER 
AS 
BEGIN 
    DECLARE @mWeightThreshold FLOAT; SET @mWeightThreshold = 0.7; 
    DECLARE @mNuMChars INT; SET @mNumChars = 4; 
    DECLARE @lLen1 int; SET @lLen1 = LEN(@stringOne) 
    DECLARE @lLen2 int; SET @lLen2 = LEN(@stringTwo) 

    IF @lLen1 = 0 
     RETURN CASE WHEN @lLen2 = 0 THEN 1 ELSE 0 END 

    DECLARE @lSearchRange int; SET @lSearchRange = dbo.InlineMax(0,dbo.InlineMax(@lLen1, @lLen2)/2 - 1); 

    DECLARE @lMatched1 TABLE (position int not null, [status] bit not null) 
    DECLARE @lMatched2 TABLE (position int not null, [status] bit not null) 

    DECLARE @lNumCommon int; SET @lNumCommon = 0 
    DECLARE @i int; SET @i = 1; WHILE(@i <= @lLen1) 
    BEGIN 
     DECLARE @lStart int; SET @lStart = dbo.InlineMax(1, @i - @lSearchRange) 
     DECLARE @lEnd int; SET @lEnd = dbo.InlineMin(@i + @lSearchRange + 1, @lLen2) 

     DECLARE @j int; SET @j = @lStart; WHILE(@j <= @lEnd) 
     BEGIN 
      IF((SELECT [status] FROM @lMatched2 WHERE position = @j) = 1) 
      BEGIN 
       SET @j = @j + 1 
       CONTINUE 
      END 

      IF (SELECT SUBSTRING(@stringOne, @i, 1)) <> (SELECT SUBSTRING(@stringTwo, @j, 1)) 
      BEGIN 
       SET @j = @j + 1 
       CONTINUE 
      END 

      INSERT INTO @lMatched1 (position, [status]) VALUES(@i, 1) 
      INSERT INTO @lMatched2 (position, [status]) VALUES(@j, 1) 

      SET @lNumCommon = @lNumCommon + 1 
      BREAK 
     END 

     SET @i = @i + 1 
    END 

    IF @lNumCommon = 0 
    BEGIN 
     RETURN 0.0; 
    END 

    DECLARE @lNumHalfTransposed int; SET @lNumHalfTransposed = 0 
    DECLARE @k INT; SET @k = 1; 
    DECLARE @stopLoop bit; SET @stopLoop = 0; 
    SET @i = 1; WHILE(@i <= @lLen1) 
    BEGIN 
     IF ((SELECT [status] FROM @lMatched1 WHERE position = @i) = 1) 
     BEGIN 
      SET @i = @i + 1 
      CONTINUE; 
     END 

     WHILE(@stopLoop = 0) 
     BEGIN 
      IF((SELECT [status] FROM @lMatched2 WHERE position = @k) = 0) 
       SET @k = @k + 1 
      ELSE 
       BREAK 

      IF((SELECT SUBSTRING(@stringOne, @i, 1)) <> (SELECT SUBSTRING(@stringTwo, @k, 1))) 
       SET @lNumHalfTransposed = @lNumHalfTransposed + 1 

      SET @k = @k + 1 
     END 

     SET @i = @i + 1 
    END 

    DECLARE @lNumTransposed INT; SET @lNumTransposed = @lNumHalfTransposed/2; 

    DECLARE @lNumCommonD FLOAT; SET @lNumCommonD = @lNumCommon 
    DECLARE @lWeight FLOAT; SET @lWeight = (@lNumCommonD/@lLen1 + @lNumCommonD/@lLen2 + (@lNumCommon - @lNumTransposed)/@lNumCommonD)/3.0; 

    IF(@lWeight <= @mWeightThreshold) 
     RETURN @lWeight 
    DECLARE @lMax INT; SET @lMax = dbo.InlineMin(@mNumChars, dbo.InlineMin(@lLen1, @lLen2)) 
    DECLARE @lPos INT; SET @lPos = 0 
    WHILE(@lPos < @lMax AND (SELECT SUBSTRING(@stringOne, @lPos, 1)) = (SELECT SUBSTRING(@stringTwo, @lPos, 1))) 
    BEGIN 
     SET @lPos = @lPos + 1 
    END 

    IF @lPos = 0 
     RETURN @lWeight 

    RETURN @lWeight + 0.1 * @lPos * (1.0 - @lWeight) 
END; 
GO