How Can I Efficiently Concatenate SQL Query Results into a Single String?

Concatenating SQL Query Results into a Single String

In a SQL scenario, it can be advantageous to consolidate query results into a cohesive string. To achieve this, one approach commonly utilized by C# programmers is the FOR EACH loop. However, SQL offers an alternative solution to accomplish this task.

One method that has proven effective is the implementation of FOR XML PATH & STUFF. This technique is particularly suitable for SQL Server 2005 and subsequent versions.

The syntax for this approach is as follows:

DECLARE @CodeNameString varchar(100)

SELECT 
   @CodeNameString = STUFF( (SELECT ',' + CodeName 
                             FROM dbo.AccountCodes 
                             ORDER BY Sort
                             FOR XML PATH('')), 
                            1, 1, '')

The FOR XML PATH('') function concatenates the string results into a single XML entity. Subsequently, the STUFF function removes the initial comma using a "nothing" character, ultimately producing the desired concatenated string.

Handling Special Characters

It is important to note that the FOR XML PATH('') approach may encounter challenges when handling special characters such as , or &. In such cases, an alternative solution is to implement the STRING_AGG() function, proposed by @KM in the original discussion.

Resource Considerations

It is worth considering that the STRING_AGG() approach requires more resources and processing time compared to the FOR XML PATH & STUFF technique. Therefore, it is crucial to assess the appropriate solution based on the specific requirements of the situation.

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