Question

While in Management Studio, I am trying to run a query/do a join between two linked servers.
Is this a correct syntax using linked db servers:

select foo.id 
from databaseserver1.db1.table1 foo, 
     databaseserver2.db1.table1 bar 
where foo.name=bar.name

Basically, do you just preface the db server name to the db.table ?

Answer 1

The format should probably be:

<server>.<database>.<schema>.<table>

For example:
DatabaseServer1.db1.dbo.table1

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Update: I know this is an old question and the answer I have is correct; however, I think any one else stumbling upon this should know a few things.

Namely, when querying against a linked server in a join situation the ENTIRE table from the linked server will likely be downloaded to the server the query is executing from in order to do the join operation. In the OP’s case, both table1 from DB1 and table1 from DB2 will be transferred in their entirety to the server executing the query, presumably named DB3.

If you have large tables, this may result in an operation that takes a long time to execute. After all it is now constrained by network traffic speeds which is orders of magnitude slower than memory or even disk transfer speeds.

If possible, perform a single query against the remote server, without joining to a local table, to pull the data you need into a temp table. Then query off of that.

If that’s not possible then you need to look at the various things that would cause SQL server to have to load the entire table locally. For example using GETDATE() or even certain joins. Others performance killers include not giving appropriate rights.

See http://thomaslarock.com/2013/05/top-3-performance-killers-for-linked-server-queries/ for some more info.