Answer
NULL represents missing or unknown data. It is not equal to zero or an empty string and requires IS NULL or IS NOT NULL for checks.
Quick Answer
NULL represents unknown or missing value - it's not zero or empty string. NULL != NULL (comparing NULL to anything yields NULL, not true/false). Use IS NULL or IS NOT NULL to check. In aggregate functions: COUNT(*) counts all rows, COUNT(col) skips NULLs. NULL values sort last in ASC order. COALESCE(col, "default") returns a fallback when the column is NULL.
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SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ