Cross db request #40

Summary

Support cross-database requests/queries.

Motivation

It would be useful to execute requests across multiple databases without requiring manual data movement or application-side joins.

Expected behavior

• Ability to reference multiple databases in a single request.
• Clear syntax and documentation.
• Proper permission checks across databases.
• Good performance and predictable transaction behavior.

Use cases

• Cross-database reporting.
• Data migration and synchronization.
• Joining data stored in separate databases.