SQL UNION vs UNION ALL

What this solves

Combine two plant extracts into one report. This pattern is useful when the business question is clear but a generic tutorial is too abstract.

The rule

UNION removes duplicates; UNION ALL keeps every row and is usually cheaper.

SELECT Material FROM PlantA
UNION ALL
SELECT Material FROM PlantB;

Real-work checklist

1. Define the business key and expected grain before writing the formula, query or markup.
2. Test the pattern on a small known sample where you can verify the answer manually.
3. Check missing values, duplicates and data types before trusting a large result.
4. Scale to the real file or database only after the logic is proven.

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