MySQL: Querying multiple databases at once

Question

I have WordPress instances with each in its own database. For an update I need to query all active plugins, that are stored in a table 'wp_options' and accessible via

WHERE option_name='active_plugins'

How can I access all active plugin settings (spread over multiple databases) and output them in one single SQL result? I know the database.tablename syntax, but how do I go on from there with the above Where statement?

A request in a single database would look like this:

SELECT option_value
  FROM `database`.`wp_options`
 WHERE option_name="active_plugins"

Answer 1

SELECT option_value
 FROM `database1`.`wp_options`
  WHERE option_name="active_plugins"
UNION
SELECT option_value
 FROM `database2`.`wp_options`
  WHERE option_name="active_plugins"