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Introduction:

Have you ever encountered a column of data with multiple unknown spaces and wanted to convert them into a single space? This is a common problem that many SQL Server users face. In this article, we will explore a set-based method to solve this problem without the need for loops or user-defined functions.

The Problem:

Let’s say you have a column of data that contains multiple unknown spaces. For example:

OriginalString
--------------
  This      has multiple   unknown                 spaces in        it.
So                     does                      this!
As                                does                        this
This, that, and the other  thing.
This needs no repair.

The goal is to convert the sections of multiple spaces of unknown length to a single space each. However, there are some additional requirements. You can’t make the data any bigger during the process because it might exceed the maximum size for the column, and you can’t use VARCHAR(MAX) because you’re using SQL Server 2000.

The Method Explained:

We can solve this problem by establishing and replacing simple patterns in a set-based fashion. Let’s use the letter “O” to represent a visible space and the letter “X” to represent a modified space. Here’s how the method works:

1. Identify pairs of spaces by modifying the second space in each pair to be an “unlikely” character. For example, we can change “OO” to “OX”.
2. Replace all occurrences of “XO” with nothing.
3. Replace all “X” characters with nothing.

By following these steps, we can convert all sets of multiple spaces to just a single space without the use of loops or user-defined functions.

The Code:

Here’s the code that accomplishes the three steps as three nested REPLACE functions:

SELECT REPLACE(
            REPLACE(
                REPLACE(
                    LTRIM(RTRIM(OriginalString))
                ,'  ',' '+CHAR(7))  --Changes 2 spaces to the OX model
            ,CHAR(7)+' ','')        --Changes the XO model to nothing
        ,CHAR(7),'') AS CleanString
FROM [YourTableName]
WHERE CHARINDEX('  ',OriginalString) > 0

Make sure to replace [YourTableName] with the actual name of your table.

Unlikely Characters and Collation:

When selecting an “unlikely character” for the “X” of the “OX” model, be cautious about the collation settings. Some characters may have equivalent treatment in certain collations, leading to unintended results. For example, the Thorn (þ) character is treated as equal to “th” in the Latin1_General_CI_AI collation.

Conclusion:

Even seemingly complex tasks like condensing multiple adjacent spaces to a single space can be accomplished without loops. By using a set-based approach, we can achieve high performance and avoid the need for loops or user-defined functions. Next time you encounter a problem that seems impossible to solve without a loop, take another look. There’s usually a better way.

Thank you for reading!

–[Your Name]