I thought it couldn't be done. I'd searched for it across the web. Terms such as mysql query multiple databases turned up nuthin' - that's right, not just nothing, but _flat-out_nuthin'_.

Today I was speaking with Matt Westgate of Lullabot about the challenges of managing 60+ Drupal web sites on a single codebase with each site having its own database, and Matt (who has a Drupal book coming out) mentioned liking MySQL for the fact that you could query multiple databases with a single query.