SQL Server Performance Forum – Threads Archive

cost of cross database queries

We are trying to decide if our new database should be separate or combined with an existing one. The two will share information and we don’t have too much experience regarding the performance of cross database queries. Does anyone have any opinions regarding performance differences between queries that reference data in a single database verses data across two databases? Would the performance be the same? Also, our product supports MS-SQL Server and Oracle (either, or, not both at the same time). Would the cost be different for each RDBMS? Any help here would be much appreciated.

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Both database are in same or differents servers?
Luis Martin …Thus mathematics may be defined as the subject in which we never know what we are talking about, nor whether what we are saying is true.
Bertrand Russell

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Ok. I gess there is no big difference one way or another.
Of course look for permissions from one database accesing the other consume some time.
I suggest, if you can, to test both ideas.
Anyway regarding this matter and RDBMS, wait others post and oppinions.
Luis Martin …Thus mathematics may be defined as the subject in which we never know what we are talking about, nor whether what we are saying is true.
Bertrand Russell

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Performance of cross-database queries shouldn’t have much of an impact. You can tweek your queries considerably if you create appropriate indexes (use index tuning wizard to do this unless you know what to look for) and manage your filegroups well. Rik

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