PSB (2/17/2015)
The query performance is very poor . Any tips on improving performance ?
I'm not particularly surprised. A few questions.
1. How often does this query run?
2. Would it be possible to introduce a flag column (indexed) containing a date when the process hit specific records, as a way to exclude those on a future run?
3. How many rows are in the table?
4. Have you tried breaking the MERGE into a standard "upsert" type of operation (that's an INSERT separate from UPDATE)?
My thought question: Have you ever been told that your query runs too fast?
My advice:
INDEXing a poor-performing query is like putting sugar on cat food. Yeah, it probably tastes better but are you sure you want to eat it?
The path of least resistance can be a slippery slope. Take care that fixing your fixes of fixes doesn't snowball and end up costing you more than fixing the root cause would have in the first place.
Need to UNPIVOT? Why not CROSS APPLY VALUES instead?[/url]
Since random numbers are too important to be left to chance, let's generate some![/url]
Learn to understand recursive CTEs by example.[/url]
[url url=http://www.sqlservercentral.com/articles/St