<a href="http://g.adspeed.net/ad.php?do=clk&zid=15220&wd=468&ht=60&pair=as" target="_blank"><img style="border:0px;" src="http://g.adspeed.net/ad.php?do=img&zid=15220&wd=468&ht=60&pair=as" alt="i" width="468" height="60"/></a>
Log in
::
Register
::
Not logged in
Home
Tags
Articles
Editorials
Stairways
Forums
Scripts
Videos
Blogs
QotD
Books
Ask SSC
SQL Jobs
Training
Authors
About us
Contact us
Newsletters
Write for us
<a href="http://g.adspeed.net/ad.php?do=clk&zid=15491&wd=120&ht=300&pair=as" target="_top"><img style="border:0px;" src="http://g.adspeed.net/ad.php?do=img&zid=15491&wd=120&ht=300&pair=as" alt="i" width="120" height="300"/></a>
Recent Posts
Recent Posts
Popular Topics
Popular Topics
Home
Search
Members
Calendar
Who's On
Home
»
Article Discussions
»
Article Discussions by Author
»
Discuss content posted by jghali
»
Computed Columns
46 posts, Page 2 of 5
««
1
2
3
4
5
»
»»
Computed Columns
Rate Topic
Display Mode
Topic Options
Author
Message
Ninja's_RGR'us
Ninja's_RGR'us
Posted Wednesday, July 21, 2010 6:23 AM
SSC-Insane
Group: General Forum Members
Last Login: Yesterday @ 7:02 PM
Points: 21,376,
Visits: 9,584
One more vote for the definitly use more ressource "issue thingie".
Using C or a+b in the query will have no difference at all. There will be a small hit if you have a udf that does (a+b) without selecting from the base tables. But you'll get a massive hit if you query data from other tables.
So, again, definitly is iffie at best without context.
Other than that awesome question.
Post #956288
jghali
jghali
Posted Wednesday, July 21, 2010 6:32 AM
SSC-Addicted
Group: General Forum Members
Last Login: Friday, November 09, 2012 12:51 AM
Points: 429,
Visits: 187
Sorry about the ambiguous answer.
What I was trying to get to is...
Retrieving data from a normal column is much faster then having to calculate the value every time a computed field is called.
Can you imagine, if you are calling 100 000 rows including a computed column? It would definitely take more resources specially if the computed column comes from other tables via UDFs...
I have to admit that the "Always" in the answer might have made the answer ambiguous... maybe it should have said "in most cases"
We now use the computed columns here with caution... We only reference computed columns in procedures for which we know will never return many many rows.
Post #956296
jghali
jghali
Posted Wednesday, July 21, 2010 6:45 AM
SSC-Addicted
Group: General Forum Members
Last Login: Friday, November 09, 2012 12:51 AM
Points: 429,
Visits: 187
I also would like to add.
The QoD is a great way to learn... I've learned so much answering and reading answers.
I would like to thank SQLServerCentral for this great service.
I say this because many people are very fast on the trigger in blasting the questions and answers not reading what has already been written in the comments section... It isn't easy to write a question and far more difficult to please everyone... I don't mind the Instructive comments I actually like them very much as we learn a lot more there too... So I would like to thank all of your comments... they were instructive to some point.
In my case, I don't really care about points, there's nothing more interesting than feeding the brain...
I love it!!!
Thanks again for all your comments and take care
Post #956303
Ninja's_RGR'us
Ninja's_RGR'us
Posted Wednesday, July 21, 2010 6:49 AM
SSC-Insane
Group: General Forum Members
Last Login: Yesterday @ 7:02 PM
Points: 21,376,
Visits: 9,584
That's one of the biggest challenges when writting a question. Everything depends in sql server when talking about performance. And if you give out too many details then the right answer(s) becomes extremely obvious.
Post #956309
pjdiller
pjdiller
Posted Wednesday, July 21, 2010 6:52 AM
SSC-Addicted
Group: General Forum Members
Last Login: Thursday, May 02, 2013 10:26 AM
Points: 404,
Visits: 274
How can one get it right without taking all morning...? I have other things to do too.
Percentage that got it right when I took it was a handsome 3%. Though, I think most know what a computed column is all about.
Take it with a grain of salt. I still respect anyone who takes the time to put a question together.
Post #956310
Duncan Pryde
Duncan Pryde
Posted Wednesday, July 21, 2010 6:56 AM
Hall of Fame
Group: General Forum Members
Last Login: Friday, June 14, 2013 2:30 AM
Points: 3,063,
Visits: 1,335
jghali (7/21/2010)
I also would like to add.
The QoD is a great way to learn... I've learned so much answering and reading answers.
I would like to thank SQLServerCentral for this great service.
I say this because many people are very fast on the trigger in blasting the questions and answers not reading what has already been written in the comments section... It isn't easy to write a question and far more difficult to please everyone... I don't mind the Instructive comments I actually like them very much as we learn a lot more there too... So I would like to thank all of your comments... they were instructive to some point.
In my case, I don't really care about points, there's nothing more interesting than feeding the brain...
I love it!!!
Thanks again for all your comments and take care
I agree with pretty much all of this. Thanks again for the question, and I hope you'll be encouraged to do more. I have to say that personally, I prefer this type of question to the "What will be the result of this query" type questions, and it may be that this type is more difficult to compose. I'll have to try doing a couple myself one day.
Keep up the good work.
Duncan
Post #956315
JF1081
JF1081
Posted Wednesday, July 21, 2010 7:59 AM
SSC-Addicted
Group: General Forum Members
Last Login: Tuesday, December 07, 2010 8:13 AM
Points: 436,
Visits: 322
Lol, I saw the word "definitely" and immediately thought: nope, it depends. I have no substantial backing for that thought as I know nothing about computed columns, but I definitely know that nothing is definite.
Post #956359
OCTom
OCTom
Posted Wednesday, July 21, 2010 8:18 AM
SSCrazy
Group: General Forum Members
Last Login: Today @ 7:16 AM
Points: 2,030,
Visits: 2,869
It's a great question and something that needed research on my part. Thanks for the question.
Has anyone used computed columns and why?
Thanks.
Post #956378
forjonathanwilson
forjonathanwilson
Posted Wednesday, July 21, 2010 8:20 AM
Valued Member
Group: General Forum Members
Last Login: Tuesday, September 14, 2010 8:24 AM
Points: 69,
Visits: 33
I got it right, and I think that the question was pretty obviously referring to CPU resources on access of the field. A calculated field is not going to be A+B, because thats just a stupid test case. More likely a computed field will be connected to a UDF and be gathering data from elsewhere. So yes, it will be a hit on every access as opposed to initial write only.
Post #956379
Chad Crawford
Chad Crawford
Posted Wednesday, July 21, 2010 8:20 AM
SSCrazy
Group: General Forum Members
Last Login: Yesterday @ 1:31 PM
Points: 2,558,
Visits: 17,421
Thanks for the question Jghali. Didn't know about the UDF part, so I picked up something new today!
Chad
Post #956380
« Prev Topic
|
Next Topic »
46 posts, Page 2 of 5
««
1
2
3
4
5
»
»»
Permissions
You
cannot
post new topics.
You
cannot
post topic replies.
You
cannot
post new polls.
You
cannot
post replies to polls.
You
cannot
edit your own topics.
You
cannot
delete your own topics.
You
cannot
edit other topics.
You
cannot
delete other topics.
You
cannot
edit your own posts.
You
cannot
edit other posts.
You
cannot
delete your own posts.
You
cannot
delete other posts.
You
cannot
post events.
You
cannot
edit your own events.
You
cannot
edit other events.
You
cannot
delete your own events.
You
cannot
delete other events.
You
cannot
send private messages.
You
cannot
send emails.
You
may
read topics.
You
cannot
rate topics.
You
cannot
vote within polls.
You
cannot
upload attachments.
You
may
download attachments.
You
cannot
post HTML code.
You
cannot
edit HTML code.
You
cannot
post IFCode.
You
cannot
post JavaScript.
You
cannot
post EmotIcons.
You
cannot
post or upload images.
Copyright © 2002-2013 Simple Talk Publishing. All Rights Reserved.
Privacy Policy.
Terms of Use.
Report Abuse.
