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How would you optimize a slow-running SQL query?

General/Othermedium0.2 min readPremium

**Process**: (1) EXPLAIN plan—analyze execution; (2) Indexing—filter/join columns; (3) Statistics—UPDATE STATISTICS; (4) Refactor—CTEs vs subqueries; (5) Partition pruning; (6) Join order, types. Example: index on user_id; EXISTS vs IN; LIMIT....

🤖 Analyze Your Answer
Frequency
Low
Asked at 1 company
Category
243
questions in General/Other
Difficulty Split
151E|43M|49H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Wipro
Key Concepts Tested
joinpartitionsql

Why This Question Matters

This medium-level General/Other question appears frequently in data engineering interviews at companies like Wipro. While less common, it tests deeper understanding that distinguishes strong candidates. Mastering the underlying concepts (join, partition, sql) 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
39 words

Process: (1) EXPLAIN plan—analyze execution; (2) Indexing—filter/join columns; (3) Statistics—UPDATE STATISTICS; (4) Refactor—CTEs vs subqueries; (5) Partition pruning; (6) Join order, types. Example: index on user_id; EXISTS vs IN; LIMIT. Measure before/after; biggest bottleneck first; avoid over-indexing (write cost).

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 General/Other 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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