Replace duplicate spaces with a single space in T-SQL

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?

Even tidier:

select string = replace(replace(replace(' select   single       spaces',' ','<>'),'><',''),'<>',' ')

Output:

> select single spaces

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

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

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

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.

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.

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

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.

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'

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.

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 !
*/

Please Find below code

select trim(string_agg(value,' ')) from STRING_SPLIT('  single    spaces   only  ',' ')
where value<>' '

This worked for me.. Hope this helps...

You can try this:

select Regexp_Replace('single    spaces   only','( ){2,}', ' ') from dual;

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     ')