Replace duplicate spaces with a single space in T-SQL - sql-server

Question

I need to ensure that a given field does not have more than one space (I am not concerned about all white space, just space) between characters.
So
'single spaces only'
needs to be turned into
'single spaces only'
The below will not work
select replace('single spaces only',' ',' ')
as it would result in
'single spaces only'
I would really prefer to stick with native T-SQL rather than a CLR based solution.
Thoughts?

Answer 1

Even tidier:
select string = replace(replace(replace(' select single spaces',' ','<>'),'><',''),'<>',' ')
Output:
select single spaces

Answer 2

This would work:
declare #test varchar(100)
set #test = 'this is a test'
while charindex(' ',#test ) > 0
begin
set #test = replace(#test, ' ', ' ')
end
select #test

Answer 3

If you know there won't be more than a certain number of spaces in a row, you could just nest the replace:
replace(replace(replace(replace(myText,' ',' '),' ',' '),' ',' '),' ',' ')
4 replaces should fix up to 16 consecutive spaces (16, then 8, then 4, then 2, then 1)
If it could be significantly longer, then you'd have to do something like an in-line function:
CREATE FUNCTION strip_spaces(#str varchar(8000))
RETURNS varchar(8000) AS
BEGIN
WHILE CHARINDEX(' ', #str) > 0
SET #str = REPLACE(#str, ' ', ' ')
RETURN #str
END
Then just do
SELECT dbo.strip_spaces(myText) FROM myTable

Answer 4

This is somewhat brute force, but will work
CREATE FUNCTION stripDoubleSpaces(#prmSource varchar(max)) Returns varchar(max)
AS
BEGIN
WHILE (PATINDEX('% %', #prmSource)>0)
BEGIN
SET #prmSource = replace(#prmSource ,' ',' ')
END
RETURN #prmSource
END
GO
-- Unit test --
PRINT dbo.stripDoubleSpaces('single spaces only')
single spaces only

Answer 5

update mytable
set myfield = replace (myfield, ' ', ' ')
where charindex(' ', myfield) > 0
Replace will work on all the double spaces, no need to put in multiple replaces. This is the set-based solution.

Answer 6

It can be done recursively via the function:
CREATE FUNCTION dbo.RemSpaceFromStr(#str VARCHAR(MAX)) RETURNS VARCHAR(MAX) AS
BEGIN
RETURN (CASE WHEN CHARINDEX(' ', #str) > 0 THEN
dbo.RemSpaceFromStr(REPLACE(#str, ' ', ' ')) ELSE #str END);
END
then, for example:
SELECT dbo.RemSpaceFromStr('some string with many spaces') AS NewStr
returns:
NewStr
some string with many spaces
Or the solution based on method described by #agdk26 or #Neil Knight (but safer)
both examples return output above:
SELECT REPLACE(REPLACE(REPLACE('some string with many spaces'
, ' ', ' ' + CHAR(7)), CHAR(7) + ' ', ''), ' ' + CHAR(7), ' ') AS NewStr
--but it remove CHAR(7) (Bell) from string if exists...
or
SELECT REPLACE(REPLACE(REPLACE('some string with many spaces'
, ' ', ' ' + CHAR(7) + CHAR(7)), CHAR(7) + CHAR(7) + ' ', ''), ' ' + CHAR(7) + CHAR(7), ' ') AS NewStr
--but it remove CHAR(7) + CHAR(7) from string
How it works:
Caution:
Char/string used to replace spaces shouldn't exist on begin or end of string and stand alone.

Answer 7

Here is a simple function I created for cleaning any spaces before or after, and multiple spaces within a string. It gracefully handles up to about 108 spaces in a single stretch and as many blocks as there are in the string. You can increase that by factors of 8 by adding additional lines with larger chunks of spaces if you need to. It seems to perform quickly and has not caused any problems in spite of it's generalized use in a large application.
CREATE FUNCTION [dbo].[fnReplaceMultipleSpaces] (#StrVal AS VARCHAR(4000))
RETURNS VARCHAR(4000)
AS
BEGIN
SET #StrVal = Ltrim(#StrVal)
SET #StrVal = Rtrim(#StrVal)
SET #StrVal = REPLACE(#StrVal, ' ', ' ') -- 16 spaces
SET #StrVal = REPLACE(#StrVal, ' ', ' ') -- 8 spaces
SET #StrVal = REPLACE(#StrVal, ' ', ' ') -- 4 spaces
SET #StrVal = REPLACE(#StrVal, ' ', ' ') -- 2 spaces
SET #StrVal = REPLACE(#StrVal, ' ', ' ') -- 2 spaces (for odd leftovers)
RETURN #StrVal
END

Answer 8

Method #1
The first method is to replace extra spaces between words with an uncommon symbol combination as a temporary marker. Then you can replace the temporary marker symbols using the replace function rather than a loop.
Here is a code example that replaces text within a String variable.
DECLARE #testString AS VARCHAR(256) = ' Test text with random* spacing. Please normalize this spacing!';
SELECT REPLACE(REPLACE(REPLACE(#testString, ' ', '*^'), '^*', ''), '*^', ' ');
Execution Time Test #1: In ten runs of this replacement method, the average wait time on server replies was 1.7 milliseconds and total execution time was 4.6 milliseconds.
Execution Time Test #2: The average wait time on server replies was 1.7 milliseconds and total execution time was 3.7 milliseconds.
Method #2
The second method is not quite as elegant as the first, but also gets the job done. This method works by nesting four (or optionally more) replace statements that replace two blank spaces with one blank space.
DECLARE #testString AS VARCHAR(256) = ' Test text with random* spacing. Please normalize this spacing!';
SELECT REPLACE(REPLACE(REPLACE(REPLACE(#testString,' ',' '),' ',' '),' ',' '),' ',' ')
Execution Time Test #1: In ten runs of this replacement method, the average wait time on server replies was 1.9 milliseconds and total execution time was 3.8 milliseconds.
Execution Time Test #2: The average wait time on server replies was 1.8 milliseconds and total execution time was 4.8 milliseconds.
Method #3
The third method of replacing extra spaces between words is to use a simple loop. You can do a check on extra spaces in a while loop and then use the replace function to reduce the extra spaces with each iteration of the loop.
DECLARE #testString AS VARCHAR(256) = ' Test text with random* spacing. Please normalize this spacing!';
WHILE CHARINDEX(' ',#testString) > 0
SET #testString = REPLACE(#testString, ' ', ' ')
SELECT #testString
Execution Time Test #1: In ten runs of this replacement method, the average wait time on server replies was 1.8 milliseconds and total execution time was 3.4 milliseconds.
Execution Time Test #2: The average wait time on server replies was 1.9 milliseconds and total execution time was 2.8 milliseconds.

Answer 9

This is the solution via multiple replace, which works for any strings (does not need special characters, which are not part of the string).
declare #value varchar(max)
declare #result varchar(max)
set #value = 'alpha beta gamma delta xyz'
set #result = replace(replace(replace(replace(replace(replace(replace(
#value,'a','ac'),'x','ab'),' ',' x'),'x ',''),'x',''),'ab','x'),'ac','a')
select #result -- 'alpha beta gamma delta xyz'

Answer 10

You can try this:
select Regexp_Replace('single spaces only','( ){2,}', ' ') from dual;

Answer 11

Just Adding Another Method-
Replacing Multiple Spaces with Single Space WITHOUT Using REPLACE in SQL Server-
DECLARE #TestTable AS TABLE(input VARCHAR(MAX));
INSERT INTO #TestTable VALUES
('HAPPY NEWYEAR 2020'),
('WELCOME ALL !');
SELECT
CAST('<r><![CDATA[' + input + ']]></r>' AS XML).value('(/r/text())[1] cast as xs:token?','VARCHAR(MAX)')
AS Expected_Result
FROM #TestTable;
--OUTPUT
/*
Expected_Result
HAPPY NEWYEAR 2020
WELCOME ALL !
*/

Answer 12

Found this while digging for an answer:
SELECT REPLACE(
REPLACE(
REPLACE(
LTRIM(RTRIM('1 2 3 4 5 6'))
,' ',' '+CHAR(7))
,CHAR(7)+' ','')
,CHAR(7),'') AS CleanString
where charindex(' ', '1 2 3 4 5 6') > 0
The full answer (with explanation) was pulled from: http://techtipsbysatish.blogspot.com/2010/08/sql-server-replace-multiple-spaces-with.html
On second look, seems to be just a slightly different version of the selected answer.

Answer 13

Please Find below code
select trim(string_agg(value,' ')) from STRING_SPLIT(' single spaces only ',' ')
where value<>' '
This worked for me..
Hope this helps...

Answer 14

With the "latest" SQL Server versions (Compatibility level 130) you could also use string_split and string_agg.
string_split can return an ordinal column when provided with a third argument. (https://learn.microsoft.com/en-us/sql/t-sql/functions/string-split-transact-sql?view=sql-server-ver16#enable_ordinal). So we can preserve the order of the string_split.
Using a common table expression:
with cte(value) as (select value from string_split(' a b c d e ', ' ', 1) where value <> '' order by ordinal offset 0 rows)
select string_agg(value, ' ') from cte
a b c d e results in a b c d e

Answer 15

I use FOR XML PATH solution to replace multiple spaces into single space
The idea is to replace spaces with XML tags
Then split XML string into string fragments without XML tags
Finally concatenating those string values by adding single space characters between two
Here is how final UDF function can be called
select dbo.ReplaceMultipleSpaces(' Sample text with multiple space ')