View vs Join

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View vs Join

Christopher Stobbs

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Points: 21098
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July 15, 2008 at 2:42 am

#193905

Hi all,
I have a view with 2 inner joins and 4 left joins returning 25 Columns, 8 of which are calculated.
My question is this.
I always thought that views acted like tables, meaning that if I called this view and even though I'm only using 2 columns it doesn't affect the performance of the view.
Therefor, should I still use the view for just returning 2 columns or should I extract the logic/query from the view and add it to my new query to get my results?
Thanks
Chris
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Try to learn something about everything and everything about something. - Thomas Henry Huxley
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Christopher Stobbs SSC-Insane Points: 21098 More actions · Answer 1

HI All,

Did some testing.

Join on View:

CPU time: 15Elapsed Time 27

Logical Reads 453 (from on 6 tables)

Join on Extracted Logic:

CPU time: 16 Elapsed Time 312

Logical Reads 457(from on 10 tables)

The logical reads on the last one is confusing cause my query only has 7 tables in the join ?

Is this once again because the view is already planned or what ever when it's created?

Thanks

Chris

----------------------------------------------
Try to learn something about everything and everything about something. - Thomas Henry Huxley

:w00t:
Posting Best Practices[/url]
Numbers / Tally Tables[/url]

SQL-4-Life

Christopher Stobbs SSC-Insane Points: 21098 More actions · Answer 2

Hi all,

WEll the results above are not 100% as I had the query plan that skewed my numbers.

Here is what I have now.

With View:

CPU Time:16

Elapsed Time:16

Logical Reads:451

Scan Count:2

Without View:

CPU Time:16

Elapsed Time:15

Logical Reads:447

Scan Count:3

So I'm still not sure which is better?

thanks

Chris

----------------------------------------------
Try to learn something about everything and everything about something. - Thomas Henry Huxley

:w00t:
Posting Best Practices[/url]
Numbers / Tally Tables[/url]

SQL-4-Life

Michael Earl-395764 SSC Guru Points: 53873 More actions · Answer 3

A view is just a stored query. They are cached and perform the same as if you just ran the query itself unless you have schema-bound and indexed it.

So, if you create a view and use it in a query or put the query the view is based on in a sub-query, they are going to perform the same. The optimizer will make sure of this. The big down side to using views is often they are re-used but not all of the joins or columns are needed. When you do this, you incur a bit of unnecessary overhead. Usually, if you re-create the logic you can get better results because you will not need to include all of the tables or columns in the view. On the other hand, re-creating logic repeatedly is bad because if you have to make a change, you have to make it in multiple places. So, seek balance.

Grant Fritchey SSC Guru Points: 398890 More actions · Answer 4

Take a look at the execution plan. Usually (and there are exceptions) you'll see that a query with a view and a query without a view, both of which reference the same tables, in the same order, with the same join criteria, will generate very similar or identical plans.

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Christopher Stobbs SSC-Insane Points: 21098 More actions · Answer 5

Thanks for all the advice everyone 🙂

----------------------------------------------
Try to learn something about everything and everything about something. - Thomas Henry Huxley

:w00t:
Posting Best Practices[/url]
Numbers / Tally Tables[/url]

SQL-4-Life