SQL – Federico Razzoli

Optimising or fixing SQL queries: how to ask for help

If you need free help or paid support, you should phrase your questions correctly and provide the necessary information.

Does NULL mean “no value”? Or does it mean “an unknown value”? Its semantics and history are ambiguous and inconsistent.

Any comparison involving at least one NULL operand will return NULL. However, SQL supports operators to easily write NULL-safe comparisons.