March 25, 2008 at 6:38 am
Hi,
There is always this notion that count(1) is better than count(*) but i have read in an article that both performs the same way. Can anybody clear on this.
Thanx in advance,
Balamurugan G
March 25, 2008 at 6:58 am
I've just tested both on a table containing 4.7 million rows and I get the exact same io stats for both:
Scan count 5, logical reads 8283, physical reads 4, read-ahead reads 8180, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
The cpu time and the elapsed times vary between different executions but they're roughly the same (around 850ms) give or take 50ms.
Seems like there's no difference there but I'd be curious if this isn't always the case.
March 26, 2008 at 6:04 am
Hi,
Can you please tell me how did you got IO stats for just one query.
I'm new to SQL and am trying to learn some techniques for Performance Tuning. I believe this could be of great help in future.
Thanks
Ankit
March 26, 2008 at 6:36 am
Ankit Mathur (3/26/2008)
Hi,Can you please tell me how did you got IO stats for just one query.
I'm new to SQL and am trying to learn some techniques for Performance Tuning. I believe this could be of great help in future.
Thanks
Ankit
Ankit,
You can enable IO/Time statistics like so:
set statistics io on
set statistics time on
Note that the statistics will remain on for the connection until you set the to off, or you close the connection.
March 26, 2008 at 9:11 am
Shouldn't be any difference.
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