The Triple Update

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The Triple Update

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call.copse SSCoach Points: 18064 More actions · Answer 1

Jeff Moden wrote:

call.copse wrote:
Jeff Moden wrote:
...
Heh... I wonder how many people actually got this question right without having to run the code?
Even I knew about quirky update and I'm only a lowly developer. Surprised Steve wasn't familiar, guess it's a bit niche.
You, good Sir, are neither "only" nor "lowly". 😀

Jeff Moden has noticed me! Sorry, I'm not some kind of fanboi but that has made my (extremely unpleasant otherwise) day.

Jeff Moden SSC Guru Points: 1004432 More actions · Answer 2

Magnus Ahlkvist wrote:

This is fun code to test and try to get ones head around - in which orders are operators applied.
DECLARE @i INT=0;
UPDATE t SET @i = id = @i + 1
SELECT @i;

Just be careful with that. It's not guaranteed to work in the proper order without following some pretty strict rules.

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

Lynn Pettis SSC Guru Points: 442467 More actions · Answer 3

Rune Bivrin wrote:

Interesting, but I'd be wary of using it. In a multi-row update, the result is pretty much undefined, unless all the rows are updated to the same value. And in that case, there isn't much point in the approach anyway, unless you really want to confuse the reader...

I have used this to capture intermediate calculations that were used in subsequent calculations in the same row of data. I wish I could find the thread here on SSC that I did this to help on OP, but it was so long ago.

SQLWinther SSCertifiable Points: 6294 More actions · Answer 4

That was interesting!

/Håkan Winther
MCITP:Database Developer 2008
MCTS: SQL Server 2008, Implementation and Maintenance
MCSE: Data Platform