Started with the obvious GROUP BY event_type plus a COUNT and ORDER BY count DESC with LIMIT 1, which is fine.
Start by clarifying the question: do they want the single most frequent event_type, or all event types ranked by frequency? Then write a query that groups by event_type, counts occurrences, orders by count descending, and limits to the top result. Consider edge cases like ties and whether to use COUNT(*) or COUNT(DISTINCT user_id) based on the definition of 'occurs'.
Pro tip: Mention that in production, you'd likely use a window function like RANK() or DENSE_RANK() to handle ties gracefully, and discuss the trade-offs between readability and performance for large datasets.
Ask whether they want the single top event_type or a ranked list, and confirm how to handle ties. Also clarify if 'occurs most frequently' means total events or unique users.
Use GROUP BY event_type with COUNT(*) to get frequencies, then ORDER BY count DESC and LIMIT 1 to get the top event type.
If ties are possible, use a window function like RANK() or DENSE_RANK() to return all top event types. Also consider NULL event_types and empty tables.
Mention indexing on event_type, and compare approaches like using a subquery with MAX(count) versus window functions. Consider if the table is partitioned by time.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.