My SQL Function is not returning the value I expected - sql

Question

This was my first attempt at a SQL function. I wrote it in VB and it works like a charm. When I translated it to SQL Server, it returns not what I expect. What the function is intended to do is to return a percentage match of two strings.
How I expected it to function is this:
accept two strings, compare the two, and based on my rating values, return a percentage of the match value...matchscore/max possiblescore
The length of the larger string is multiplied by 3. This is the max possiblescore.
Go character by character of the first string and find that character in the second string.
If the character is found in the same position in the second string, add three to the matchscore and move on to the next letter.
If the character is found in the second word, but not in the same position, add one to match score and move on to the next character.
If the character is not found in the second string, add nothing and move on to the next character.
Divide the matchscore by the max possiblescore. This returns a decimal value. I read RETURN only returns an integer, so I multiplied the division result by 100.
An example of what I expected is I compare "CAT" to "CART". My expected return is 7/12...0.58. Instead, I get 0. If I compare "CAT" to "CAT", I expect 9/9...1.00. Instead, I get 2.
(Note from 9/17/2014: I appreciate your input. I used what you suggested, and did one more major change, that doesn't affect what I asked about, other than getting the correct final answer is that I got rid of the second While Loop. Instead, I search for #strLetter in #strWord2. If it is found, then, I look to see if it is in the same position in #strWord2 as #strWord1. If it is, then I add 3, if not, I add 1. This sped up the function and made the count accurate.
Here is the code:
CREATE FUNCTION [dbo].[CompareWords]
(#strWord1 VARCHAR(2000), #strWord2 VARCHAR(2000))
RETURNS DECIMAL
AS
BEGIN
SET #strWord1 = UPPER(#strWord1)
SET #strWord2 = UPPER(#strWord2)
DECLARE #intLength INT
IF LEN(#strWord1) >= LEN(#strWord2)
BEGIN
SET #intLength = LEN(#strWord1)
END
ELSE
BEGIN
SET #intLength = LEN(#strWord2)
END
DECLARE #iWordLoop1 INT
DECLARE #iWordLoop2 INT
DECLARE #intWordLoop2 INT
DECLARE #intWordScore INT
DECLARE #intLetterScore INT
SET #intWordScore = 0
SET #intWordLoop2 = Len(#strWord2)
DECLARE #strLetter VARCHAR(1000)
DECLARE #count1 INT
SET #count1 = 0
SET #iWordLoop1 = Len(#strWord1)
WHILE (#count1 < #iWordLoop1)
BEGIN
SET #strLetter = SUBSTRING(#strWord1, #count1+1, 1)
SET #intLetterScore = 0
DECLARE #count2 INT
SET #count2 = 0
SET #iWordLoop2 = Len(#strWord2)
WHILE (#count2 < #iWordLoop2)
BEGIN
If #strLetter = SUBSTRING(#strWord2, #count2+1, 1)
BEGIN
If #iWordLoop1 = #iWordLoop2
BEGIN
SET #intLetterScore = 3
SET #iWordLoop2 = Len(#strWord2)
END
ELSE
BEGIN
SET #intLetterScore = 1
END
END
SET #intWordScore = #intWordScore + #intLetterScore
SET #count2 = (#count2 + 1)
END
SET #count1 = (#count1 + 1)
END
DECLARE #sinScore DEC
SET #sinScore = (#intWordScore / (3 * #intLength)) * 100
RETURN #sinSCore
END;

Answer 1

The most significant changes I made were to
reset the intLetterScore to 0 after it's been used in the intWordScore calculation. Without it being reset, the same value was being used each time the inner loop and the character was not matched.
move the multiplication by 100 into the
brackets in the calculation of sinScore.
As referred to in a previous post, because you are doing integer multiplication, the decimal portion is truncated from the calculation. By growing the wordScore by a factor of 100, it is much more likely to be larger than the length and yield a result which is non-zero.
Multiplying outside the brackets has the multiplies the integer result of the division score by length. If this answer is already zero, then the multiplication result is also zero.
Other changes I made are commented in the code: the variable intWordLoop2 has no effect on the calculation and can be removed; strLetter can be declared as a Char(1) instead of VarChar(1000).
CREATE FUNCTION [dbo].[CompareWords]
(#strWord1 VARCHAR(2000), #strWord2 VARCHAR(2000))
RETURNS DECIMAL
AS
BEGIN
SET #strWord1 = UPPER(#strWord1)
SET #strWord2 = UPPER(#strWord2)
--Set #intLength (maxLength as len of word1 or word2)
DECLARE #intLength INT --maxLength
IF LEN(#strWord1) >= LEN(#strWord2)
BEGIN
SET #intLength = LEN(#strWord1)
END
ELSE
BEGIN
SET #intLength = LEN(#strWord2)
END
DECLARE #iWordLoop1 INT, #iWordLoop2 INT--, #intWordLoop2 INT --This variable doesn't impact the calculation
DECLARE #intWordScore INT
DECLARE #intLetterScore INT
SET #intWordScore = 0
--SET #intWordLoop2 = Len(#strWord2)--this value is not used anywhere else, so removing makes no difference.
--DECLARE #strLetter VARCHAR(1000)
DECLARE #strLetter CHAR(1)--there is no need for 1000 characters since we're only ever assigning a single character to this
DECLARE #count1 INT
SET #count1 = 0
SET #iWordLoop1 = Len(#strWord1)
WHILE (#count1 < #iWordLoop1)
BEGIN
SET #strLetter = SUBSTRING(#strWord1, #count1+1, 1)
SET #intLetterScore = 0
DECLARE #count2 INT
SET #count2 = 0
SET #iWordLoop2 = Len(#strWord2)
WHILE (#count2 < #iWordLoop2)
BEGIN
If #strLetter = SUBSTRING(#strWord2, #count2+1, 1)
BEGIN
If #iWordLoop1 = #iWordLoop2
BEGIN
SET #intLetterScore = 3
SET #iWordLoop2 = Len(#strWord2)
END
ELSE
BEGIN
SET #intLetterScore = 1
END
END
SET #intWordScore = #intWordScore + #intLetterScore
SET #intLetterScore = 0
SET #count2 = (#count2 + 1)
END
SET #count1 = (#count1 + 1)
END
DECLARE #sinScore DEC
SET #sinScore = (#intWordScore*100 / (3 * #intLength))
RETURN #sinSCore
END;
select dbo.comparewords ('Cat','cart')