referencing 2 different DBs in a single query

[sneakyimp]

I just tried a query like this in phpMyAdmin and it seemed to work just fine:

SELECT t1.*, t2.* FROM db1.some_table t1, db2.some_table t2 WHERE t2.field1=t1.field2

I am guessing this means I'll be able to write queries that join tables from two separate dbs in my code using the mysql_* functions. Is that so?

If so, I'm sort of wondering mysql_select_db is really just a matter of convenience -- kind of like the working directory concept in linux. You don't have to type in the database name for every table because the current db is assumed. Do I have that right?

I'm also assuming that if I connect to a db as userX, then in any query, I can reference any table in any db for which userX has the right permissions. Is that correct?

[NogDog]

I hadn't been aware that MySQL supported this until I read your post, then saw this in the manual. So it would appear (but I've not tried it yet!) that you should be able to do that, and that the mysql_select_db() is only necessary to set the default DB that will be used if you do not provide a database prefix.

[Piranha]

I have used different databases in one query from Java without problems, the query being a normal SQL query. It defenetley works, but I don't think it is as fast as it would be having both tables in the same database.

Unfortunatley I haven't used it in PHP, and don't know how you should handle it in the script.