Reviewed by Aditya Kumar · Last reviewed 2026-03-24
BigQuery nested: STRUCT for nested objects; REPEATED for arrays. Example: SELECT user.id, event.name FROM t, UNNEST(t.events) event. STRUCT: user.name, user.address.city. REPEATED: ARRAY_AGG, UNNEST. Query nested: t.user.name; repeated: SELECT id, e FROM t, UNNEST(events) e....
BigQuery nested: STRUCT for nested objects; REPEATED for arrays. Example: SELECT user.id, event.name FROM t, UNNEST(t.events) event. STRUCT: user.name, user.address.city. REPEATED: ARRAY_AGG, UNNEST. Query nested: t.user.name; repeated: SELECT id, e FROM t, UNNEST(events) e. Best: use STRUCT for hierarchical data; REPEATED for one-to-many. Avoid over-nesting; flatten when it simplifies queries. Why it matters: Design choices compound at scale—wrong approach can cause 100× overhead. Scalability trade-offs: Profile before optimizing; validate on sample then full. Cost implications: Suboptimal choices multiply at billion-row scale.
Red Flag: Generic textbook answers. Pro-Move: 'At scale we measured X, implemented Y, achieved Z%—validated and iterated.'
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