Fed? Brain? I hate to think what you would call me.

OK, my point was that if the Code is already a candidate key in a table, why not throw away the Id and make Code the clustered PK? Could give...

Do the Id columns in these tables perform any useful function? Based on what you've posted so far, it looks like there's an argument for removing them ... or maybe...

A WHILE loop is a really slow way of generating this. Instead, consider using something like this, which does it fast! (Once again, thanks to Jeff Moden for the base...

This is likely to be a permissions issue. The user executing the command (which will be the SQL Agent service user, by default) needs appropriate access to all of the...

Do you receive any error messages?

Yes. In SSIS, you have access to C#, allowing very sophisticated levels of manipulation to be accomplished. But...

Thanks, Jeff. I made the assumption that the OP did not have a table 'TBL' containing a single column 'COLUMN1' and therefore that the addition of a suitable PK would...

Another version:

SELECT t.COLUMN1
      ,STRING_AGG (s.Item, ',') WITHIN GROUP(ORDER BY s.ItemNumber DESC)
FROM @TBL t
    CROSS APPLY
(SELECT * FROM dbo.DelimitedSplit8K (t.COLUMN1,...

Frederico, Des thank you both for the examples. Taught me something new … appreciated.

Please script...

Also, if the %of duplicates is higher than the % of singles, then it may be better to copy the singles into a new table and switch out the...

You could also include a copy of the query here (use a Code block for formatting)

People here will need a lot more information before they can provide any sort of detailed assistance.

A good starting point will be to paste a copy of your actual execution...

It would be helpful if you could post your test data in consumable format, eg

DROP TABLE IF EXISTS #SomeTab;

CREATE TABLE #SomeTab(...)

INSERT #SomeTab(...)
SELECT ...

and also show us what...