Basics & SELECT Queries · SQL SQL
How does SQL handle NULL values when comparing them with standard comparison operators like equals (=) or not equals (<>) in a WHERE clause?
Practice question from Basics & SELECT Queries (SQL SQL), with the correct answer and a step-by-step solution.
medium · MCQ · Q-9AAE6F
How does SQL handle NULL values when comparing them with standard comparison operators like equals (=) or not equals (<>) in a WHERE clause?
- A.NULL is treated as equivalent to zero.
- B.NULL is treated as an empty string.
- C.Any comparison with NULL evaluates to UNKNOWN, resulting in no rows matched.Correct answer
- D.Standard comparison operators automatically evaluate NULL as true.
Solution
In SQL three-valued logic, NULL represents missing or unknown data. Any standard comparison with NULL yields UNKNOWN, so the WHERE clause filters out those rows. The IS NULL or IS NOT NULL operators must be used instead.
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