Not equal <> != operator on NULL

Question

Could someone please explain the following behavior in SQL?

SELECT * FROM MyTable WHERE MyColumn != NULL (0 Results)
SELECT * FROM MyTable WHERE MyColumn <         


        

Answer 1

In SQL, anything you evaluate / compute with NULL results into UNKNOWN

This is why SELECT * FROM MyTable WHERE MyColumn != NULL or SELECT * FROM MyTable WHERE MyColumn <> NULL gives you 0 results.

To provide a check for NULL values, isNull function is provided.

Moreover, you can use the IS operator as you used in the third query.

Hope this helps.