How do you handle NULL-safe comparisons in SQL Server?

Short answer: Normal = does not match NULLs. Use IS NULL / IS NOT NULL, or ISNULL/COALESCE for display defaults. For “both NULL or equal”, use EXISTS patterns or INTERSECT, or (a = b OR (a IS NULL AND b IS NULL)).

Three-valued logic (TRUE/FALSE/UNKNOWN) is a classic theory follow-up.