How do you query semi-structured data (JSON) in SQL, and when should you flatten vs keep it nested?

Modern warehouses store JSON natively, and querying it well separates strong data engineers from the rest. The signal is path access plus unnesting, and a clear call on when to flatten hot fields versus keep the schema-on-read flexibility.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.