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SQL: Remove whitespace from in between text

I need to convert

"Hello         how   are       you                                               doing     "

to

"Hello how are you doing"

I tried the following, but that just removes ALL whitespace. I still need the sentence to look normal to include the regular single space between words:

 SELECT REPLACE('Hello         how   are       you                                               doing     ' ,CHAR(32),'')
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pzozulka
Asked:
pzozulka
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4 Solutions
 
jogosCommented:
If a lot of spaces a lot of recursions can occur as a rule then you can limit it by replacing multiple spaces at each recursion
CREATE FUNCTION dbo.RemoveMultipleSpaces (@str NVARCHAR(MAX))
    RETURNS NVARCHAR(MAX)
AS
BEGIN
    IF CHARINDEX('  ', @str) = 0
        RETURN @str;
    RETURN dbo.RemoveMultipleSpaces( REPLACE( REPLACE(@str, '       ', ' '), '  ', ' ') );
END
GO

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Scott PletcherSenior DBACommented:
Someone discovered another method that is faster: embedded replaces of power(2) + 1 spaces with a single space.


SELECT
    REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(LTRIM(RTRIM(string)),
        SPACE(33), SPACE(1)), SPACE(17), SPACE(1)), SPACE(9), SPACE(1)), SPACE(5), SPACE(1)),
        SPACE(3), SPACE(1)), SPACE(2), SPACE(1)), SPACE(2), SPACE(1))
FROM (
    SELECT 'Hello         how   are       you                                               doing     ' AS string
) AS test_data
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pzozulkaAuthor Commented:
Does anyone see a problem with the below?
declare @STRING  varchar(100) 
set @STRING =  'Hello         how   are       you                                               doing     '  
set @STRING = REPLACE(REPLACE(REPLACE(@STRING
    ,CHAR(32),'øù')
    ,'ùø','')
    ,'øù',CHAR(32))

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Scott PletcherSenior DBACommented:
The correct version of that method/technique would work, it's just significantly slower than the method I posted earlier.
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pzozulkaAuthor Commented:
The mothod you posted seems to also implicitly performing ltrim and rtrim, is that correct?
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Scott PletcherSenior DBACommented:
It's explicitly performing an LTRIM and RTRIM.  You can remove that if you want to.
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PortletPaulCommented:
The method proposed by yourself at ID: 40350768 assumes that the replacement string pairs used by the replace function do not occur in the source string. If that is not true then the result will be inaccurate.

øù          spaces replaced by this to form:   øùøùøùøùøùøùøùøù
ùø          middle portion ùøùøùøùøùøùøùø then replaced, resulting in:   øù
øù          then replaced by 1 space

The replacements occur by character pairs, the method suggested by Scott works in larger units and does not rely on characters that might occur in the string (except the unwanted spaces).
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Vitor MontalvãoMSSQL Senior EngineerCommented:
Just replace two spaces ('  ') for nothing (''):
SELECT LTRIM(RTRIM(REPLACE('Hello         how   are       you                                               doing     ' ,'  ','')))

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Sameer Ahamed SatharCommented:
Vitor,

In this scenario your solution get failed

SELECT LTRIM(RTRIM(REPLACE('Hello         how   are       you                                                                        doing     ' ,'  ',''))) from dual;

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Pzozulka,

You can use simple regexp_replace function to achieve your requirement.If you feel that you will get spaces before "Hello" also,you can add a TRIM before the same.

DECLARE
  v_txt VARCHAR2(1000);
BEGIN
  SELECT TRIM(regexp_replace('          Hello    how      are         you                doing                         ','[[:space:]]+',chr(32)))
  INTO v_txt
  FROM dual;
  
  dbms_output.put_line(v_txt);
END;

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- SAM
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PortletPaulCommented:
@Sameer seems are you  suggesting Oracle syntax (but the question specifies MS SQL Server in topics)
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Sameer Ahamed SatharCommented:
Hi PortletPaul,

It seems the question is for oracle only.As all the comments given was related to that.Need author's reply regarding this.
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Vitor MontalvãoMSSQL Senior EngineerCommented:
@Sameer, what for you added "FROM dual"? I tested it before posting and worked perfectly.
This question is in MS SQL Server area and only have tags to SQL Server. And the code it's pretty much T-SQL.
But of course, the author can clarify this.
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PortletPaulCommented:
There has been no mention of Oracle, or Oracle syntax, until the first post by Sameer. I see no reason at all to assume this is for Oracle, quite the reverse, IF TSQL was equipped with regexp_replace we would not be wasting our time arguing over how best to use replace.

and nor would the asker have chosen  BOTH MS SQL Server  & SQL Server 2008
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pzozulkaAuthor Commented:
This is for TSQL.
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pzozulkaAuthor Commented:
Thanks all for your input. I implemented Scott's suggestion, and it seems to not perform any better or worse than the solution I posted. The example I originally gave was just that -- an example.

In reality, all I need it for is to get rid of 1 to 3 whitespaces in between text. So it is highly unlikely that I will ever need to remove powers of 2 + 1 whitespaces.

Having said that, would my posted solution work better for smaller whitespace removals? Since it uses less REPLACE functions?
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Scott PletcherSenior DBACommented:
You seem to strongly prefer it, so use it.  Until/unless you have large amounts of data, you won't notice any performance hit anyway.  The odds of a stray ø or ù are probably low enough to ignore.
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Vitor MontalvãoMSSQL Senior EngineerCommented:
@pzozulka, my solution didn't fits in what you wanted?
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Scott PletcherSenior DBACommented:
No, Vitor, it doesn't.  Here's your code against a different input string:

SELECT LTRIM(RTRIM(REPLACE('Hello  how  are  you  doing   ' ,'  ','')))
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Vitor MontalvãoMSSQL Senior EngineerCommented:
I see. Works for his example but you just gave me a case that will fail.
Thanks Scott. Will try to work on it.
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Scott PletcherSenior DBACommented:
Your code requires that the extra spaces must appear only in odd numbers: 3, 5, 7, etc..  Needless to say, data is not likely to cooperate with that requirement :-) .
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