Learn SQL: Complete Roadmap

Always clarify the question first — ask about edge cases, expected output, and scale.

Think aloud during the interview. Explain your approach before writing code.

Start with the simplest query that works, then refactor for performance.

Always check for NULLs, ties, empty tables, and duplicates in your answer.

Use EXPLAIN to show you think about performance, not just correctness.

Know SQL execution order cold: FROM → JOIN → WHERE → GROUP BY → HAVING → SELECT → ORDER BY.