If you don't know where to look, it's a bit hard to find the database schema for the Stack Exchange Data Explorer (both new and old). As far as I can tell, the Stack Exchange Data Explorer only provides one clue—in the "About" page—as to the whereabouts of the data schema.
The Stack Exchange trilogy data dumps are hosted at ClearBits!. You can subscribe via RSS and be notified every time a new dump is available. Have fun remixing and reusing; all we ask is for proper attribution.
However, I would argue that this answer on Meta Stack Overflow provides the most accessible overview of the database schema. Can someone add this to the Data Explorer FAQ or show at least show me where it is prominently displayed on a Data Explorer page?