How to replace all special characters in string - sql

Question

I have a table with the following columns:
dbo.SomeInfo
- Id
- Name
- InfoCode
Now I need to update the above table's InfoCode as
Update dbo.SomeInfo
Set InfoCode= REPLACE(Replace(RTRIM(LOWER(Name)),' ','-'),':','')
This replaces all spaces with - & lowercase the name
When I do check the InfoCode, I see there are Names with some special characters like
Cathe Friedrich''s Low Impact
coffeyfit-cardio-box-&-burn
Jillian Michaels: Cardio
Then I am manually writing the update sql against this as
Update dbo.SomeInfo
SET InfoCode= 'cathe-friedrichs-low-impact'
where Name ='Cathe Friedrich''s Low Impact '
Now, this solution is not realistic for me. I checked the following links related to Regex & others around it.
UPDATE and REPLACE part of a string
https://www.codeproject.com/Questions/456246/replace-special-characters-in-sql
But none of them is hitting the requirement.
What I need is if there is any character other [a-z0-9] replace it - & also there should not be continuous -- in InfoCode
The above Update sql has set some values of InfoCode as the-dancer's-workout®----starter-package
Some Names have value as
Sleek Technique™
The Dancer's-workout®
How can I write Update sql that could handle all such special characters?

Answer 1

Using NGrams8K you could split the string into characters and then rather than replacing every non-acceptable character, retain only certain ones:
SELECT (SELECT '' + CASE WHEN N.token COLLATE Latin1_General_BIN LIKE '[A-z0-9]'THEN token ELSE '-' END
FROM dbo.NGrams8k(V.S,1) N
ORDER BY position
FOR XML PATH(''))
FROM (VALUES('Sleek Technique™'),('The Dancer''s-workout®'))V(S);
I use COLLATE here as on my default collation in my instance the '™' is ignored, therefore I use a binary collation. You may want to use COLLATE to switch the string back to its original collation outside of the subquery.

Answer 2

This approach is fully inlinable:
First we need a mock-up table with some test data:
DECLARe #SomeInfo TABLE (Id INT IDENTITY, InfoCode VARCHAR(100));
INSERT INTO #SomeInfo (InfoCode) VALUES
('Cathe Friedrich''s Low Impact')
,('coffeyfit-cardio-box-&-burn')
,('Jillian Michaels: Cardio')
,('Sleek Technique™')
,('The Dancer''s-workout®');
--This is the query
WITH cte AS
(
SELECT 1 AS position
,si.Id
,LOWER(si.InfoCode) AS SourceText
,SUBSTRING(LOWER(si.InfoCode),1,1) AS OneChar
FROM #SomeInfo si
UNION ALL
SELECT cte.position +1
,cte.Id
,cte.SourceText
,SUBSTRING(LOWER(cte.SourceText),cte.position+1,1) AS OneChar
FROM cte
WHERE position < DATALENGTH(SourceText)
)
,Cleaned AS
(
SELECT cte.Id
,(
SELECT CASE WHEN ASCII(cte2.OneChar) BETWEEN 65 AND 90 --A-Z
OR ASCII(cte2.OneChar) BETWEEN 97 AND 122--a-z
OR ASCII(cte2.OneChar) BETWEEN 48 AND 57 --0-9
--You can easily add more ranges
THEN cte2.OneChar ELSE '-'
--You can easily nest another CASE to deal with special characters like the single quote in your examples...
END
FROM cte AS cte2
WHERE cte2.Id=cte.Id
ORDER BY cte2.position
FOR XML PATH('')
) AS normalised
FROM cte
GROUP BY cte.Id
)
,NoDoubleHyphens AS
(
SELECT REPLACE(REPLACE(REPLACE(normalised,'-','<>'),'><',''),'<>','-') AS normalised2
FROM Cleaned
)
SELECT CASE WHEN RIGHT(normalised2,1)='-' THEN SUBSTRING(normalised2,1,LEN(normalised2)-1) ELSE normalised2 END AS FinalResult
FROM NoDoubleHyphens;
The first CTE will recursively (well, rather iteratively) travers down the string, character by character and a return a very slim set with one row per character.
The second CTE will then GROUP the Ids. This allows for a correlated sub-query, where the actual check is performed using ASCII-ranges. FOR XML PATH('') is used to re-concatenate the string. With SQL-Server 2017+ I'd suggest to use STRING_AGG() instead.
The third CTE will use a well known trick to get rid of multiple occurances of a character. Take any two characters which will never occur in your string, I use < and >. A string like a--b---c will come back as a<><>b<><><>c. After replacing >< with nothing we get a<>b<>c. Well, that's it...
The final SELECT will cut away a trailing hyphen. If needed you can add similar logic to get rid of a leading hyphen. With v2017+ There was TRIM('-') to make this easier...
The result
cathe-friedrich-s-low-impact
coffeyfit-cardio-box-burn
jillian-michaels-cardio
sleek-technique
the-dancer-s-workout

Answer 3

You can create a User-Defined-Function for something like that.
Then use the UDF in the update.
CREATE FUNCTION [dbo].LowerDashString (#str varchar(255))
RETURNS varchar(255)
AS
BEGIN
DECLARE #result varchar(255);
DECLARE #chr varchar(1);
DECLARE #pos int;
SET #result = '';
SET #pos = 1;
-- lowercase the input and remove the single-quotes
SET #str = REPLACE(LOWER(#str),'''','');
-- loop through the characters
-- while replacing anything that's not a letter to a dash
WHILE #pos <= LEN(#str)
BEGIN
SET #chr = SUBSTRING(#str, #pos, 1)
IF #chr LIKE '[a-z]' SET #result += #chr;
ELSE SET #result += '-';
SET #pos += 1;
END;
-- SET #result = TRIM('-' FROM #result); -- SqlServer 2017 and beyond
-- multiple dashes to one dash
WHILE #result LIKE '%--%' SET #result = REPLACE(#result,'--','-');
RETURN #result;
END;
GO
Example snippet using the function:
-- using a table variable for demonstration purposes
declare #SomeInfo table (Id int primary key identity(1,1) not null, InfoCode varchar(100) not null);
-- sample data
insert into #SomeInfo (InfoCode) values
('Cathe Friedrich''s Low Impact'),
('coffeyfit-cardio-box-&-burn'),
('Jillian Michaels: Cardio'),
('Sleek Technique™'),
('The Dancer''s-workout®');
update #SomeInfo
set InfoCode = dbo.LowerDashString(InfoCode)
where (InfoCode LIKE '%[^A-Z-]%' OR InfoCode != LOWER(InfoCode));
select *
from #SomeInfo;
Result:
Id InfoCode
-- -----------------------------
1 cathe-friedrichs-low-impact
2 coffeyfit-cardio-box-burn
3 jillian-michaels-cardio
4 sleek-technique-
5 the-dancers-workout-