views, unions and different dbs

[George Kosmidis]

Hello everyone,
I have a problem which as it seems I cannot find a way to work around:

Let's say I have two dbs dbA and dbB, and a table in each: dbA.tbl and dbB.tbl.
I also have a third DB which that has a view with union all of the two tables:
CREATE VIEW vTbls AS
SELECT * FROM dbA.tbl
UNION ALL
SELECT * FROM dbB.tbl

In order to have a way of seperating each record in the view I add a column in the view that describes each row:

CREATE VIEW vTbls AS
SELECT 'dbA' AS db ,dbA.tbl.* FROM dbA.tbl
UNION ALL
SELECT 'dbB' AS db ,dbB.tbl.* FROM dbB.tbl

As anyone could expect, it's very very slow to perform a query or a join with this view, and you could imagine that a join between two similar views could be a hell.
Is there a way to work around this problem?

(The real case senario now is that dbA and dbB are eshops, and the third db is the admin db which has to have a way of outputing summaries of both eshops.)

Thank you all.