#sql null

5 Powerful Thoughts on SQL NULLs

USA IT JOBS

NULL BASICS:

An arithmetic operation involving a NULL returns NULL. For example, NULL minus NULL yields NULL, not zero.

A boolean comparison between two values involving a NULL returns neither true nor false, but unknown in SQL’s three-valued logic. For example, neither NULL equals NULL nor NULL not-equals NULL is true. Testing whether a value is NULL requires an expression such as IS…