How does SQL Server handle NULL values in comparisons?

Question

Pankajkumar Patel · Answer

Hi Sandhiya Priya, In SQL Server, NULL represents unknown or missing value. It behaves differently in comparisons than regular values. Comparison with NULL using operators such as =, , , etc. will returns UNKNOWN. It will not return TRUE or FALSE. SELECT CASE WHEN NULL = NULL THEN 'True' ELSE 'False' END AS Result; Output: False Using IS NULL and IS NOT NULL is the only reliable ways to test for NULL WHERE column IS NULL WHERE column IS NOT NULL Hope this will help you!

Uttam Chaturvedi · Answer

SQL Server, NULL represents an unknown or missing value, and it behaves differently from regular values. SELECT * FROM Student WHERE StudentID = NULL; You might expect it to find rows where StudentID is NULL — but it won’t return anything. That’s because NULL = NULL is not TRUE; it’s UNKNOWN (since you can’t be sure two unknowns are equal). So the correct way to check null values is IS NULL -- to check if a value is NULL IS NOT NULL -- to check if a value is not NULL Example: SELECT * FROM Student WHERE StudentID IS NULL;

How does SQL Server handle NULL values in comparisons?

Answers (2)