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What is a UNION ALL operator?

Q: What is a UNION ALL operator?

Short answer: The UNION ALL operator combines the result sets of two or more queries, but unlike UNION, it does not remove duplicate rows. Example code SELECT name FROM employees UNION ALL SELECT name FROM contractors; This will return all names from both employees and contractors, including duplicates. Real-world example (ShopNest) ShopNest’s SQL Server database stores customers, products, and orders. Good indexes and clear foreign keys keep checkout queries fast and safe. Say this in the interview Define — one clear sentence (the short answer above). Example — relate it to a project like ShopNest or your real work. Trade-off — when you would not use it.

Short answer: The UNION ALL operator combines the result sets of two or more queries, but unlike UNION, it does not remove duplicate rows.

Example code

SELECT name FROM employees UNION ALL SELECT name FROM contractors; This will return all names from both employees and contractors, including duplicates.

Real-world example (ShopNest)

ShopNest’s SQL Server database stores customers, products, and orders. Good indexes and clear foreign keys keep checkout queries fast and safe.

Say this in the interview

Define — one clear sentence (the short answer above).
Example — relate it to a project like ShopNest or your real work.
Trade-off — when you would not use it.

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