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. Continua a leggere 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. Continua a leggere 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. Continua a leggere What does NULL mean in SQL?