How to remove white space characters from a string in SQL Server

Question

I'm trying to remove white spaces from a string in SQL but LTRIM and RTRIM functions don't seem to work?

Column:

[ProductAlternateKey] [nvarchar](25) COLLATE Latin1_General_CS_AS NULL

Query:

select REPLACE(ProductAlternateKey, ' ', '@'),
       LEN(ProductAlternateKey),
       LTRIM(RTRIM(ProductAlternateKey))      AS LRTrim,
       LEN(LTRIM(RTRIM(ProductAlternateKey))) AS LRLen,
       ASCII(RIGHT(ProductAlternateKey, 1))   AS ASCIIR,
       ASCII(LEFT(ProductAlternateKey, 1))    AS ASCIIL,
       ProductAlternateKey
from DimProducts
where ProductAlternateKey  like '46783815%'

Result:

|  COLUMN_0 | COLUMN_1 | LRTrim | LRLen | ASCIIR | ASCIIL | PRODUCTALTERNATEKEY |
---------------------------------------------------------------------------------
|  46783815 |        8 | 46783815|     8|   53   |   52   |            46783815 |
| 46783815  |        10|46783815  |   10|   10   |   52   |           46783815  |

Can it be other symbols if LTRIM and RTRIM are not working, like "Enter"?

Answer 1

Using ASCII(RIGHT(ProductAlternateKey, 1)) you can see that the right most character in row 2 is a Line Feed or Ascii Character 10.

This can not be removed using the standard LTrim RTrim functions.

You could however use (REPLACE(ProductAlternateKey, CHAR(10), '')

You may also want to account for carriage returns and tabs. These three (Line feeds, carriage returns and tabs) are the usual culprits and can be removed with the following :

LTRIM(RTRIM(REPLACE(REPLACE(REPLACE(ProductAlternateKey, CHAR(10), ''), CHAR(13), ''), CHAR(9), '')))

If you encounter any more "white space" characters that can't be removed with the above then try one or all of the below:

--NULL
Replace([YourString],CHAR(0),'');
--Horizontal Tab
Replace([YourString],CHAR(9),'');
--Line Feed
Replace([YourString],CHAR(10),'');
--Vertical Tab
Replace([YourString],CHAR(11),'');
--Form Feed
Replace([YourString],CHAR(12),'');
--Carriage Return
Replace([YourString],CHAR(13),'');
--Column Break
Replace([YourString],CHAR(14),'');
--Non-breaking space
Replace([YourString],CHAR(160),'');

This list of potential white space characters could be used to create a function such as :

Create Function [dbo].[CleanAndTrimString] 
(@MyString as varchar(Max))
Returns varchar(Max)
As
Begin
    --NULL
    Set @MyString = Replace(@MyString,CHAR(0),'');
    --Horizontal Tab
    Set @MyString = Replace(@MyString,CHAR(9),'');
    --Line Feed
    Set @MyString = Replace(@MyString,CHAR(10),'');
    --Vertical Tab
    Set @MyString = Replace(@MyString,CHAR(11),'');
    --Form Feed
    Set @MyString = Replace(@MyString,CHAR(12),'');
    --Carriage Return
    Set @MyString = Replace(@MyString,CHAR(13),'');
    --Column Break
    Set @MyString = Replace(@MyString,CHAR(14),'');
    --Non-breaking space
    Set @MyString = Replace(@MyString,CHAR(160),'');

    Set @MyString = LTRIM(RTRIM(@MyString));
    Return @MyString
End
Go

Which you could then use as follows:

Select 
    dbo.CleanAndTrimString(ProductAlternateKey) As ProductAlternateKey
from DimProducts