Fuzzy matching on string - sql

Question

I have a question related to matching strings in a MSSQL database. Basically, I have a table that contains ICD9 and CPT codes. The issue is that the format that these codes come in is usually incorrect (i.e. too many characters, missing decimal, etc...). I need to be able to lookup the description for each of these codes from a lookup table containing the correct code.
Because of the way these codes are structured I can do some type of "progressive" match to at least find the category of the code.
Lets say the correct code is something like: 306.98
And for this example lets pretend there are no other values between 306 and 307.
I would like to strip the decimal and look for a match, one character at a time, until one is not found. Then select the last matching string.
So 306,3069,3098, 306981, 3069812, etc... would match the string 306.98.
I hope that makes sense to everyone. I am not sure how I would even begin to do this, so any suggestion would be a great help.

Answer 1

One possible solution is to strip down the code to its basic element (306) and then do a like operator:
WHERE Code LIKE '306%'

Answer 2

Use FLOOR function to strip the decimal part and then use a LIKE operator in the WHERE clause.
Something like:
SELECT <COLUMN-LIST>
FROM <TABLE-NAME>
WHERE <THE-COLUMN> LIKE CAST(FLOOR(306.09) AS VARCHAR) + '%'

Answer 3

Here you have your example.You just need to convert value to nvarchar #string.
DECLARE #string AS NVARCHAR (MAX) = '306.98';
DECLARE #Table TABLE (
TextVal NVARCHAR (MAX));
INSERT INTO #Table ([TextVal])
SELECT '4444656'
UNION ALL
SELECT '30'
UNION ALL
SELECT '3069'
UNION ALL
SELECT '306989878787'
;
WITH numbers
AS (SELECT ROW_NUMBER() OVER ( ORDER BY (SELECT 1)) AS Number
FROM [sys].[objects] AS o1 CROSS JOIN [sys].[objects] AS o2),
Chars
AS (SELECT SUBSTRING(#string, [Number], 1) AS Let,
[Number]
FROM [numbers]
WHERE [Number] <= LEN(#string)),
Joined
AS (SELECT [Let],
CAST (1 AS BIGINT) AS Number
FROM chars
WHERE [Number] = 1
UNION ALL
SELECT [J].[Let] + CASE
WHEN [Chars].[Let] = '.' THEN '' ELSE [Chars].[Let]
END AS LEt,
Chars.[Number]
FROM [Joined] AS J
INNER JOIN
[Chars]
ON [Chars].[Number] = [J].[Number] + 1)
SELECT *
FROM #Table AS T
WHERE [T].[TextVal] IN (SELECT [Let]
FROM [Joined])
OR [T].[TextVal] LIKE '%'+(SELECT TOP 1 [Let] FROM
[Joined] ORDER BY [Number] DESC ) +'%'
;
Result will be:
TextVal
30
3069
306989878787

Answer 4

I was able to figure it out. Basically, I just needed to step through each character of the string and look for a match until once was no longer found. Thanks for the help!
/* ICD9 Lookup */
USE TSiData_Suite_LWHS_V11
DECLARE #String NVARCHAR (10)
DECLARE #Match NVARCHAR(10)
DECLARE #Substring NVARCHAR (10)
DECLARE #Description NVARCHAR(MAX)
DECLARE #Length INT
DECLARE #Count INT
SET #String = '309.99999999'
/* Remove decimal place from string */
SET #String = REPLACE(#String,'.','')
/* Get lenth of string */
SET #Length = LEN(#String)
/* Initialize count */
SET #Count = 1
/* Get Substring */
SET #Substring = SUBSTRING(#String,1,#Count)
/* Start processing */
IF (#Length < 1 OR #String IS NULL)
/* Validate #String */
BEGIN
SET #Description = 'No match found for string. String is not proper length.'
END
ELSE IF ((SELECT COUNT(*) FROM LookupDiseases WHERE REPLACE(LookupCodeDesc,'.','') LIKE #Substring + '%') < 1)
/* Check for at least one match */
BEGIN
SET #Description = 'No match found for string.'
END
ELSE
/* Look for matching code */
BEGIN
WHILE ((SELECT COUNT(*) FROM ICD9Lookup WHERE REPLACE(LookupCodeDesc,'.','') LIKE #Substring + '%') <> 1 AND (#Count < #Length + 1))
BEGIN
/* Update substring value */
SET #Substring = SUBSTRING(#String,1,#Count + 1)
/* Increment #Count */
SET #Count += 1
/* Select the first matching code and get description */
SELECT TOP(1) #Match = LookupCodeDesc, #Description = LookupName FROM ICD9Lookup WHERE REPLACE(LookupCodeDesc,'.','') LIKE #Substring + '%' ORDER BY LookupCodeDesc ASC
END
END
PRINT #Match
PRINT #Description