beginnerSQL Fundamentals Deep Dive — Data Types, NULL Handling & Query Execution Order
Why does WHERE column = NULL never match any rows, even when the column genuinely contains NULLs?
NULL represents 'unknown,' not a comparable value — NULL = NULL evaluates to NULL (unknown), not TRUE, because SQL uses three-valued logic (TRUE/FALSE/UNKNOWN) and only rows evaluating to exactly TRUE are kept. The correct form is WHERE column IS NULL, which checks for the unknown state directly rather than comparing against it.
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