CREATE FUNCTION F_strcompare(@str1 VARCHAR(8000),

                             @str2 VARCHAR(8000))

RETURNS VARCHAR(10)

AS

  BEGIN

      DECLARE @i   INT,

              @j   INT,

              @k   INT,

              @ret VARCHAR(10)

      SELECT @i = MAX(strlen),

             @j = MIN(strlen),

             @k = 0

      FROM   (SELECT strlen=Len(@str1)

              UNION

              SELECT strlen=Len(@str2)) t

      IF( @j = 0 )

        RETURN '0%'

      WHILE @j > 0

        BEGIN

            IF Substring(@str1, @j, 1) = Substring(@str2, @j, 1)

              SET @k=@k + 1

            SET @j=@j - 1

        END

      SET @ret = Rtrim(CAST(@k * 100.0 / @i AS NUMERIC(3, 0))) + '%'

      RETURN @ret

  END

GO

SELECT dbo.F_strcompare('中国人','中华人民共和国')