Stairway to T-SQL DML Level 12: Using the MERGE Statement

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Stairway to T-SQL DML Level 12: Using the MERGE Statement

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boriskey Mr or Mrs. 500 Points: 511 More actions · Answer 1

i also found that performance of MERGE is a bit worse than just INSERT/UPDATE - with indexes in place - it is not a huge difference but still noticeable.

Also it is hard to debug/troubleshoot MERGE statements - with INSERT/UPDATEs you can just select the SELECT part with joins and WHERE clause and run it to see results and play with them till you are ready to do actual inserts/updates.

With Merge statement, you would have to cut out the code from it and run on a side or use output clause which you have to type or uncomment.

One pain at least in 2008, that you cannot use results on OUTPUT clause outside of the MERGE (as a inner query) - you can only insert results to a table variable which you need to define and create first.

So after some first excitements our team is back on using old good UPSERTs.

Jeff Moden SSC Guru Points: 1003863 More actions · Answer 2

Greg,

Would you respond to the following post concerning your stairway. Thanks.

http://www.sqlservercentral.com/Forums/Topic1489336-90-1.aspx

--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)

Vertigo44 SSCarpal Tunnel Points: 4055 More actions · Answer 3

I would like to get started with these...

DML:

http://www.sqlservercentral.com/stairway/75773/

Advanced T-SQL:

http://www.sqlservercentral.com/stairway/104497/

The only thing I could not determine is which version of SQL Server Express I should install and what database these are written for (ie: Adventure Works)?

Thanks!

akljfhnlaflkj SSC Guru Points: 76202 More actions · Answer 4

I don't know that much about MERGE. It sort of scares me. We've managed to create all of our stored procedures without it.