SQLCOALESCENULLtutorial
What is COALESCE in SQL? Handling NULL for beginners
COALESCE returns the first non-NULL value from a list. Plain words: defaults for missing data, fallback chains (nickname → name → 'Guest'), safe arithmetic, and pairing with NULLIF. With tables and common pitfalls.
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COALESCEreturns the first non-NULL value from a list of arguments. Essentially a fallback chain: if the first is NULL, take the second; if that's NULL too, the third; and so on.This article is currently in Russian. The full English translation is on the way.