“SELECT 1″ rather than a “SELECT *” when using an EXISTS or a NOT EXISTS clause”.

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“SELECT 1″ rather than a “SELECT *” when using an EXISTS or a NOT EXISTS clause”.

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amenjonathan

Posted Friday, February 11, 2011 1:48 PM

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I also use SELECT NULL.

Personally if something is faster and there's virtually no complexity difference, I use the faster version. Why waste where there is no need is my motto.

My SQL Server Blog

Post #1062821

luckysql.kinda

Posted Friday, February 11, 2011 4:31 PM

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Cost Analysis Among EXISTS (SELECT 1), EXISTS (SELECT COUNT(1)), EXISTS (SELECT *) AND EXISTS (SELECT TOP 1) should help

-lucky

Post #1062892

GilaMonster

Posted Saturday, February 12, 2011 1:17 AM

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luckysql.kinda (2/11/2011)

Cost Analysis Among EXISTS (SELECT 1), EXISTS (SELECT COUNT(1)), EXISTS (SELECT *) AND EXISTS (SELECT TOP 1) should help

Not really. Firstly there's no cost analysis there, no testing, no numbers, nothing other than the blogger's untested opinion, and one of the queries he lists is logically different from the others.

Gail Shaw
Microsoft Certified Master: SQL Server 2008, MVP
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
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Post #1062946

GilaMonster

Posted Saturday, February 12, 2011 1:20 AM

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amenjonathan (2/11/2011)

I also use SELECT NULL.

Personally if something is faster and there's virtually no complexity difference, I use the faster version. Why waste where there is no need is my motto.

The point is, it's not significantly faster, it's a couple of nanoseconds at best. It's micro-optimisation, it's a waste of time for no value.

Use EXISTS (Select *, EXISTS (Select 1, EXISTS (Select NULL, or any other form as they are not going to make anything resembling a noticeable difference.

Gail Shaw
Microsoft Certified Master: SQL Server 2008, MVP
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

Post #1062947

amenjonathan

Posted Monday, February 14, 2011 9:25 AM

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GilaMonster (2/12/2011)

amenjonathan (2/11/2011)

I also use SELECT NULL.

Personally if something is faster and there's virtually no complexity difference, I use the faster version. Why waste where there is no need is my motto.

If I'm typing it out for the first time and I type SELECT NULL instead of SELECT *, I don't see how that wastes any time. Yes it does not provide a lot of value, but hey a tiny amount of value for free is still better than no value for free. Also, again this is just the way I do things, it helps me stay vigilant with optimization.

Again my motto is why not do what's most optimal if it doesn't require any additional work?

My SQL Server Blog

Post #1063623

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