In linked server, which server will process data?

Question

In linked server, which server will process data?

adonetok

SSCrazy Eights

Points: 8395
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April 10, 2013 at 7:57 am

#291945

In ServerA, I created a linked server to ServerB.
In ServerA, there is a query like below.
select * from [ServerB].order.dbo.allorder where city='london'
Question:
Which server will process data?
1) processing in B and then pass the result to A
2) pass all data in A from B, process in A

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MyDoggieJessie SSC-Forever Points: 44486 More actions · Answer 1

In this scenario Server B processes it, then passes it back to Server A

______________________________________________________________________________Never argue with an idiot; Theyll drag you down to their level and beat you with experience

Lowell SSC Guru Points: 323504 More actions · Answer 2

MyDoggieJessie (4/10/2013)
In this scenario Server B processes it, then passes it back to Server A

i believe that's incorrect:

i'm pretty sure this code, Executed on server A would copy the entire table allorder into temp, and then perform the WHERE statement , and then return the results.

select * from [ServerB].order.dbo.allorder where city='london'

this would do the work on ServerB:

EXECUTE ( 'select * from order.dbo.allorder where city=''london'' ' ) AT ServerB;

Lowell

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adonetok SSCrazy Eights Points: 8395 More actions · Answer 3

Is there any way to set up linked server always run in B without this statement?

EXECUTE ( 'select * from order.dbo.allorder where city=''london'' ' ) AT ServerB;

Lowell SSC Guru Points: 323504 More actions · Answer 4

adonetok (4/10/2013)
Is there any way to set up linked server always run in B without this statement?
EXECUTE ( 'select * from order.dbo.allorder where city=''london'' ' ) AT ServerB;

Now that I'm thinking about it, the same command via OPENQUERY would perform at the remote as well: the problem with that is the same as EXECUTE AT: the query has to be hardcoded into a static string, no swapping with a variable like @sqlstatement

SELECT * FROM OPENQUERY( [ServerB],'SET FMTONLY OFF; 'select * from order.dbo.allorder where city=''london''; ')

Lowell

--help us help you! If you post a question, make sure you include a CREATE TABLE... statement and INSERT INTO... statement into that table to give the volunteers here representative data. with your description of the problem, we can provide a tested, verifiable solution to your question! asking the question the right way gets you a tested answer the fastest way possible!

MyDoggieJessie SSC-Forever Points: 44486 More actions · Answer 5

There is a very good write-up on this here

______________________________________________________________________________Never argue with an idiot; Theyll drag you down to their level and beat you with experience

ChrisM@Work SSC Guru Points: 186127 More actions · Answer 6

adonetok (4/10/2013)
In ServerA, I created a linked server to ServerB.
In ServerA, there is a query like below.
select * from [ServerB].order.dbo.allorder where city='london'
Question:
Which server will process data?
1) processing in B and then pass the result to A
2) pass all data in A from B, process in A

In addition to EXECUTE AT and OPENQUERY, you also have the REMOTE join hint, to instruct SQL Server to perform the join at the remote.

^{“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw}

For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden