**Z-ordering** (Z-order curve): Colocates related data in same files. Multi-column filter (e.g., region + date) can skip more files vs. single-column partitioning. **Delta**: OPTIMIZE table ZORDER BY (col1, col2). **Why**: Improves file pruning; columnar still scans selected...
This medium-level SQL question appears frequently in data engineering interviews at companies like Puma. While less common, it tests deeper understanding that distinguishes strong candidates. Mastering the underlying concepts (partition) will help you answer variations of this question confidently.
Break this problem into components. Identify the core trade-offs involved, then walk the interviewer through your reasoning step by step. Demonstrate awareness of edge cases and production considerations - this is what separates good answers from great ones.
Z-ordering (Z-order curve): Colocates related data in same files. Multi-column filter (e.g., region + date) can skip more files vs. single-column partitioning. Delta: OPTIMIZE table ZORDER BY (col1, col2). Why: Improves file pruning; columnar still scans selected files. Order: High-filter columns first. Combine: Partition by date + Z-order by (region, user_id). Cost: OPTIMIZE rewrites files; run periodically.
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Analyze My Answer — FreeAccording to DataEngPrep.tech, this is one of the most frequently asked SQL interview questions, reported at 1 company. DataEngPrep.tech maintains a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.