It is quite common to use an equality condition and an IS NULL condition on the same columns. Unfortunately, this could make queries very slow. Continue reading MariaDB/MySQL IS NULL conditions and indexes
SQL columns can be NULL or NOT NULL. Let’s see what are the good and bad reasons to declare NULL columns. Continue reading When to use NULLable columns in relational databases
Does NULL mean “no value”? Or does it mean “an unknown value”? Its semantics and history are ambiguous and inconsistent. Continue reading What does NULL mean in SQL?