T-SQL function for generating slugs? - tsql

Question

Quick check to see if anyone has or knows of a T-SQL function capable of generating slugs from a given nvarchar input. i.e;
"Hello World" > "hello-world"
"This is a test" > "this-is-a-test"
I have a C# function that I normally use for these purposes, but in this case I have a large amount of data to parse and turn into slugs, so it makes more sense to do it on the SQL Server rather than have to transfer data over the wire.
As an aside, I don't have Remote Desktop access to the box so I can't run code (.net, Powershell etc) against it
Thanks in advance.
EDIT:
As per request, here's the function I generally use to generate slugs:
public static string GenerateSlug(string n, int maxLength)
{
string s = n.ToLower();
s = Regex.Replace(s, #"[^a-z0-9s-]", "");
s = Regex.Replace(s, #"[s-]+", " ").Trim();
s = s.Substring(0, s.Length <= maxLength ? s.Length : maxLength).Trim();
s = Regex.Replace(s, #"s", "-");
return s;
}

Answer 1

You can use LOWER and REPLACE to do this:
SELECT REPLACE(LOWER(origString), ' ', '-')
FROM myTable
For wholesale update of the column (the code sets the slug column according to the value of the origString column:
UPDATE myTable
SET slug = REPLACE(LOWER(origString), ' ', '-')

Answer 2

This is what I've come up with as a solution. Feel free to fix / modify where needed.
I should mention that the database I'm currently developing against is case insensitive hence the LOWER(#str).
CREATE FUNCTION [dbo].[UDF_GenerateSlug]
(
#str VARCHAR(100)
)
RETURNS VARCHAR(100)
AS
BEGIN
DECLARE #IncorrectCharLoc SMALLINT
SET #str = LOWER(#str)
SET #IncorrectCharLoc = PATINDEX('%[^0-9a-z ]%',#str)
WHILE #IncorrectCharLoc > 0
BEGIN
SET #str = STUFF(#str,#incorrectCharLoc,1,'')
SET #IncorrectCharLoc = PATINDEX('%[^0-9a-z ]%',#str)
END
SET #str = REPLACE(#str,' ','-')
RETURN #str
END
Mention to: http://blog.sqlauthority.com/2007/05/13/sql-server-udf-function-to-parse-alphanumeric-characters-from-string/ for the original code.

Answer 3

I know this is an old thread, but for future generation, I found one function that deals even with accents here:
CREATE function [dbo].[slugify](#string varchar(4000))
RETURNS varchar(4000) AS BEGIN
declare #out varchar(4000)
--convert to ASCII
set #out = lower(#string COLLATE SQL_Latin1_General_CP1251_CS_AS)
declare #pi int
--I'm sorry T-SQL have no regex. Thanks for patindex, MS .. :-)
set #pi = patindex('%[^a-z0-9 -]%',#out)
while #pi>0 begin
set #out = replace(#out, substring(#out,#pi,1), '')
--set #out = left(#out,#pi-1) + substring(#out,#pi+1,8000)
set #pi = patindex('%[^a-z0-9 -]%',#out)
end
set #out = ltrim(rtrim(#out))
-- replace space to hyphen
set #out = replace(#out, ' ', '-')
-- remove double hyphen
while CHARINDEX('--', #out) > 0 set #out = replace(#out, '--', '-')
return (#out)
END

Answer 4

Here's a variation of Jeremy's response. This might not technically be slugifying since I'm doing a couple of custom things like replacing "." with "-dot-", and stripping out apostrophes. Main improvement is this one also strips out all consecutive spaces, and doesn't strip out preexisting dashes.
create function dbo.Slugify(#str nvarchar(max)) returns nvarchar(max)
as
begin
declare #IncorrectCharLoc int
set #str = replace(replace(lower(#str),'.',' dot '),'''','')
-- remove non alphanumerics:
set #IncorrectCharLoc = patindex('%[^0-9a-z -]%',#str)
while #IncorrectCharLoc > 0
begin
set #str = stuff(#str,#incorrectCharLoc,1,' ')
set #IncorrectCharLoc = patindex('%[^0-9a-z -]%',#str)
end
-- remove consecutive spaces:
while charindex(' ',#str) > 0
begin
set #str = replace(#str, ' ', ' ')
end
set #str = replace(#str,' ','-')
return #str
end

Answer 5

I took Jeremy's response a couple steps further by removing all consecutive dashes even after spaces are replaced, and removed leading and trailing dashes.
create function dbo.Slugify(#str nvarchar(max)) returns nvarchar(max) as
begin
declare #IncorrectCharLoc int
set #str = replace(replace(lower(#str),'.','-'),'''','')
-- remove non alphanumerics:
set #IncorrectCharLoc = patindex('%[^0-9a-z -]%',#str)
while #IncorrectCharLoc > 0
begin
set #str = stuff(#str,#incorrectCharLoc,1,' ')
set #IncorrectCharLoc = patindex('%[^0-9a-z -]%',#str)
end
-- replace all spaces with dashes
set #str = replace(#str,' ','-')
-- remove consecutive dashes:
while charindex('--',#str) > 0
begin
set #str = replace(#str, '--', '-')
end
-- remove leading dashes
while charindex('-', #str) = 1
begin
set #str = RIGHT(#str, len(#str) - 1)
end
-- remove trailing dashes
while len(#str) > 0 AND substring(#str, len(#str), 1) = '-'
begin
set #str = LEFT(#str, len(#str) - 1)
end
return #str
end

Answer 6

-- Converts a title such as "This is a Test" to an all lower case string such
-- as "this-is-a-test" for use as the slug in a URL. All runs of separators
-- (whitespace, underscore, or hyphen) are converted to a single hyphen.
-- This is implemented as a state machine having the following four states:
--
-- 0 - initial state
-- 1 - in a sequence consisting of valid characters (a-z, A-Z, or 0-9)
-- 2 - in a sequence of separators (whitespace, underscore, or hyphen)
-- 3 - encountered a character that is neither valid nor a separator
--
-- Once the next state has been determined, the return value string is
-- built based on the transitions from the current state to the next state.
--
-- State 0 skips any initial whitespace. State 1 includes all valid slug
-- characters. State 2 converts multiple separators into a single hyphen
-- and skips trailing whitespace. State 3 skips any punctuation between
-- between characters and, if no additional whitespace is encountered,
-- then the punctuation is not treated as a word separator.
--
CREATE FUNCTION ToSlug(#title AS NVARCHAR(MAX))
RETURNS VARCHAR(MAX)
AS
BEGIN
DECLARE #retval AS VARCHAR(MAX) = ''; -- return value
DECLARE #i AS INT = 1; -- title index
DECLARE #c AS CHAR(1); -- current character
DECLARE #state AS INT = 0; -- current state
DECLARE #nextState AS INT; -- next state
DECLARE #tab AS CHAR(1) = CHAR(9); -- tab
DECLARE #lf AS CHAR(1) = CHAR(10); -- line feed
DECLARE #cr AS CHAR(1) = CHAR(13); -- carriage return
DECLARE #separators AS CHAR(8) = '[' + #tab + #lf + #cr + ' _-]';
DECLARE #validchars AS CHAR(11) = '[a-zA-Z0-9]';
WHILE (#i <= LEN(#title))
BEGIN
SELECT #c = SUBSTRING(#title, #i, 1),
#nextState = CASE
WHEN #c LIKE #validchars THEN 1
WHEN #state = 0 THEN 0
WHEN #state = 1 THEN CASE
WHEN #c LIKE #separators THEN 2
ELSE 3 -- unknown character
END
WHEN #state = 2 THEN 2
WHEN #state = 3 THEN CASE
WHEN #c LIKE #separators THEN 2
ELSE 3 -- stay in state 3
END
END,
#retval = #retval + CASE
WHEN #nextState != 1 THEN ''
WHEN #state = 0 THEN LOWER(#c)
WHEN #state = 1 THEN LOWER(#c)
WHEN #state = 2 THEN '-' + LOWER(#c)
WHEN #state = 3 THEN LOWER(#c)
END,
#state = #nextState,
#i = #i + 1
END
RETURN #retval;
END

Answer 7

To slug with Vietnamese unicode
CREATE function [dbo].[toslug](#string nvarchar(4000))
RETURNS varchar(4000) AS BEGIN
declare #out nvarchar(4000)
declare #from nvarchar(255)
declare #to varchar(255)
--convert to ASCII dbo.slugify
set #string = lower(#string)
set #out = #string
set #from = N'ýỳỷỹỵáàảãạâấầẩẫậăắằẳẵặéèẻẽẹêếềểễệúùủũụưứừửữựíìỉĩịóòỏõọơớờởỡợôốồổỗộđ·/_,:;'
set #to = 'yyyyyaaaaaaaaaaaaaaaaaeeeeeeeeeeeuuuuuuuuuuuiiiiioooooooooooooooood------'
declare #pi int
set #pi = 1
--I'm sorry T-SQL have no regex. Thanks for patindex, MS .. :-)
while #pi<=len(#from) begin
set #out = replace(#out, substring(#from,#pi,1), substring(#to,#pi,1))
set #pi = #pi + 1
end
set #out = ltrim(rtrim(#out))
-- replace space to hyphen
set #out = replace(#out, ' ', '-')
-- remove double hyphen
while CHARINDEX('--', #out) > 0 set #out = replace(#out, '--', '-')
return (#out)
END