SQL UNION ALL

How do we combine multiple datasets without the computational overhead of deduplication?

Advanced⏱ 3 Minutes⭐ 430 XP

🤔 THE QUESTION

How do we combine multiple datasets without the computational overhead of deduplication?

💡 WHAT IS IT?

UNION ALL concatenates result sets directly while preserving duplicates, executing much faster.

🎯 WHAT IS IT USED FOR?

High-volume data ingestion, log merging, historical append pipelines in data lakes.

💻 EXAMPLE

SELECT name
FROM employees
UNION ALL
SELECT name
FROM contractors;

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