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Explain the differences between table re-creation and ALTER TABLE operations.

SQLmedium0.5 min readPremium

**ALTER TABLE**: In-place metadata or incremental change; minimal downtime; supported for add column, drop column (some systems), rename. **Re-creation** (CTAS, DROP+CREATE): Full copy; changes storage format, clustering, partitioning; reclaims space from deletes. **Why ALTER**:...

🤖 Analyze Your Answer
Frequency
Low
Asked at 1 company
Category
487
questions in SQL
Difficulty Split
130E|271M|86H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Capco
Key Concepts Tested
partition

Why This Question Matters

This medium-level SQL question appears frequently in data engineering interviews at companies like Capco. 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.

How to Approach This

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.

Expert Answer
93 words

ALTER TABLE: In-place metadata or incremental change; minimal downtime; supported for add column, drop column (some systems), rename. Re-creation (CTAS, DROP+CREATE): Full copy; changes storage format, clustering, partitioning; reclaims space from deletes. Why ALTER: Zero-downtime schema evolution; additive changes (new column with default) are instant in most systems. Why re-create: Column type change, format migration (Parquet → Delta), defragmentation, partition strategy change. Scalability: ALTER on 10B-row table can be metadata-only (seconds) or require full rewrite (hours). Re-creation needs 2× storage during copy. Cost: ALTER is lower ops cost; re-creation often scheduled during maintenance.

The complete answer continues with detailed implementation patterns, architectural trade-offs, and production-grade considerations covering performance optimization and real-world examples.

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According 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.

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