CTE Query to CONCAT text (over 10,000 rows)

Question

I am trying to construct a CTE query to loop through rows of data and concatenate text into one line for each SampleUserNumber.

Below is what I am working with:

CREATE TABLE #SampleTable
(
SampleRowID INT IDENTITY(1,1),
SampleUserNumber INT,
SampleLineNumber INT,
SampleTextLine VARCHAR(1000)
)

Here is my CTE Query:

Here is the Output:

The CTE Query works and the result is correct, but my main issue is the performance and the amount of records I have to process. Right now I am dealing with 100,000 records at a bare minimum.

Questions:

1. Have I written the query incorrectly to handle 100,000 records? Is there a more efficient way to write the CTE?

2. Is there another way more efficient and better way to do this? [looping would be out of the question unless I have no other choice]

Sorry for all the images. I figured it would be much easier to show everything rather than write it out here.

Thank you.

Answer 1

How does this approach do in comparison?

SELECT 
  SampleUserNumber, 
  CombinedMessage = STUFF(
    (SELECT N' ' + SampleTextLine FROM #SampleTable
       WHERE SampleUserNumber = t.SampleUserNumber
       ORDER BY SampleLineNumber
       FOR XML PATH, TYPE).value(N'.[1]',N'nvarchar(max)'),1,1,'')
FROM #SampleTable AS t
GROUP BY SampleUserNumber
ORDER BY SampleUserNumber;

It would probably be useful for your #temp table to have a clustered index on SampleUserNumber, SampleLineNumber or at least a non-clustered on those two columns that INCLUDEs SampleTextLine.

In SQL Server 2017 you would be able to use a much more straightforward approach, almost guaranteed to be faster:

SELECT SampleUserNumber, 
  CombinedMessage = STRING_AGG(CONVERT(varchar(max),SampleTextLine), ' ') 
                    WITHIN GROUP (ORDER BY SampleLineNumber)
FROM #SampleTable
GROUP BY SampleUserNumber 
ORDER BY SampleUserNumber;

To avoid the CONVERT you could just make your #temp table column a MAX type.