SQL method to replace repeating blanks with single blanks

This works:

UPDATE myTable
SET myTextColumn =
    REPLACE(
        REPLACE(
            REPLACE(myTextColumn
                ,'  ',' '+CHAR(1)) -- CHAR(1) is unlikely to appear
        ,CHAR(1)+' ','')
    ,CHAR(1),'')
WHERE myTextColumn LIKE '%  %'

Entirely set-based; no loops.

So we replace any two spaces with an unusual character and a space. If we call the unusual character X, 5 spaces become: ' X X ' and 6 spaces become ' X X X'. Then we replace 'X ' with the empty string. So 5 spaces become ' ' and 6 spaces become ' X'. Then, in case there was an even number of spaces, we remove any remaining 'X's, leaving a single space.

Here is a simple set based way that will collapse multiple spaces into a single space by applying three replaces.

DECLARE @myTable TABLE (myTextColumn VARCHAR(50))

INSERT INTO @myTable VALUES ('0Space')
INSERT INTO @myTable VALUES (' 1 Spaces 1 Spaces. ')
INSERT INTO @myTable VALUES ('  2  Spaces  2  Spaces.  ')
INSERT INTO @myTable VALUES ('   3   Spaces  3   Spaces.   ')
INSERT INTO @myTable VALUES ('    4    Spaces  4    Spaces.    ')
INSERT INTO @myTable VALUES ('     5     Spaces  5     Spaces.     ')
INSERT INTO @myTable VALUES ('      6      Spaces  6      Spaces.      ')

select replace(
          replace(
             replace(
                LTrim(RTrim(myTextColumn)), ---Trim the field
             '  ',' |'),                    ---Mark double spaces
          '| ',''),                         ---Delete double spaces offset by 1
       '|','')                              ---Tidy up
       AS SingleSpaceTextColumn
 from @myTable

Your Update statement can now be set based:

 update @myTable
    set myTextColumn = replace(
                          replace(
                             replace(
                                LTrim(RTrim(myTextColumn)),
                             '  ',' |'),
                          '| ',''),
                       '|','')  

Use an appropriate Where clause to limit the Update to only the rows that have you need to update or maybe have double spaces.

Example:

where 1<=Patindex('%  %', myTextColumn)

I have found an external write up on this method: REPLACE Multiple Spaces with One

Not very SET Based but a simple WHILE would do the trick.

CREATE TABLE #myTable (myTextColumn VARCHAR(32))

INSERT INTO #myTable VALUES ('NoSpace')
INSERT INTO #myTable VALUES ('One Space')
INSERT INTO #myTable VALUES ('Two  Spaces')
INSERT INTO #myTable VALUES ('Multiple    Spaces    .')

WHILE EXISTS (SELECT * FROM #myTable WHERE myTextColumn LIKE '%  %')
  UPDATE  #myTable 
  SET     myTextColumn = REPLACE(myTextColumn, '  ', ' ') 
  WHERE   myTextColumn LIKE '%  %'

SELECT * FROM #myTable

DROP TABLE #myTable

SELECT 'starting...' --sets @@rowcount
WHILE @@rowcount <> 0
    update myTable
    set myTextColumn = replace(myTextColumn, '  ', ' ')
    where myTextColumn like '%  %'

Step through the characters one by one, and maintain a record of the previous character. If the current character is a space, and the last character is a space, stuff it.

CREATE FUNCTION [dbo].[fnRemoveExtraSpaces]  (@Number AS varchar(1000))
Returns Varchar(1000)
As
Begin
Declare @n int  -- Length of counter
Declare @old char(1)

Set @n = 1
--Begin Loop of field value
While @n <=Len (@Number)
    BEGIN
     If Substring(@Number, @n, 1) = ' ' AND @old = ' '
      BEGIN
        Select @Number = Stuff( @Number , @n , 1 , '' )
      END
     Else
      BEGIN
       SET @old = Substring(@Number, @n, 1)
       Set @n = @n + 1
      END
    END
Return @number
END
GO


select [dbo].[fnRemoveExtraSpaces]('xxx     xxx     xxx    xxx')

create table blank(
field_blank char(100))

insert into blank values('yyy      yyyy')
insert into blank values('xxxx    xxxx')
insert into blank values ('xxx    xxx')
insert into blank values ('zzzzzz zzzzz')

update blank 
set field_blank = substring(field_blank,1,charindex(' ',field_blank)-1) + ' ' + ltrim(substring(field_blank,charindex(' ',field_blank) + 1,len(field_blank)))
where CHARINDEX (' ' , rtrim(field_blank)) > 1

select * from blank

Try this:

UPDATE Ships
SET name = REPLACE(REPLACE(REPLACE(name, '  ', ' ' + CHAR(1)), CHAR(1) + ' ', ''), CHAR(1), '')
WHERE name LIKE '%  %'

REPLACE(REPLACE(REPLACE(myTextColumn,' ',' %'),'% ',''),'%','')

Statement above worked terrifically for replacing multiple spaces with a single space. Optionally add LTRIM and RTRIM to remove spaces at the beginning.

Got it from here: http://burnignorance.com/database-tips-and-tricks/remove-multiple-spaces-from-a-string-using-sql-server/

WHILE
 (SELECT count(myIDcolumn) 
  from myTable where myTextColumn like '%  %') > 0
BEGIN
  UPDATE myTable 
  SET myTextColumn = REPLACE(myTextColumn ,'  ',' ')
END

Try it:

CREATE OR REPLACE FUNCTION REM_SPACES (TEXTO VARCHAR(2000))

    RETURNS VARCHAR(2000)

    LANGUAGE SQL

    READS SQL DATA
BEGIN

    SET TEXTO = UPPER(LTRIM(RTRIM(TEXTO)));

    WHILE LOCATE('  ',TEXTO,1) >= 1 DO
        SET TEXTO = REPLACE(TEXTO,'  ',' ');
    END WHILE;

RETURN TEXTO;

END

Update myTable set myTextColumn = replace(myTextColumn, '  ', ' ');

The above query will remove all the double blank spaces with single blank space

But this would work only once.