Subject Re: [firebird-support] Multiple Database Connection
Author David Johnson
I have read this thread because I am always interested in distributed
problems and solutions.

No business problem is presented, so there is insufficient information
to recommend a single "best practice".

Firebird does not support the concept of cross-database joins. Even the
Vulcan engine (slated for FB3, last I heard) which allows multiple back-
ends, does not allow cross-database joins.

The following is not specific to firebird, zeos components, or Delphi.
It is just a set of basic considerations that applies to the root
technical problem, in the absence of a well-defined business

I frequently join across multiple incompatible data sources including
assorted RDBMS products and non-RDBMS such as VSAM.

If I need a cross-database join that is either one-shot or not
performance critical, I will often use an ODBC connection indirectly via
MS-Access to linked tables. If performance is a factor or the join is
part of a permanent system, I use a nested loop join of the results of
the queries that I need to run.

Nested loop joins are memory intensive if you expect more than a few
thousand rows in the final result set. I generally try to keep the
result sets to under a 200,000 rows per outer loop iteration.

I hope this helps.

On Mon, 2006-07-03 at 13:32 +0300, Nihat Tunali wrote:
> Hi,
> Configuration:
> - i have a four firebird database in my local/server computer.
> - In my Delphi program ,i used zeos component /other not important.
> - One database component and connected to only one database (such as
> db1)
> - In db1 database has some procedures,triggers & views
> * My question:
> - How can i connect to other databases (db2,db3, etc ) in Only SQL
> Query ?
> SELECT ........... FROM db1.table1, db2.table1 etc...????
> - How can call procedure,views and other dababase ddl functions
> SELECT ..........FROM db1.procedure1, db4.procedure1 ??????
> thanks.