NULLs are built into the algebraic and arithmetic machinery of SQL. You can see how the equality operator (=) acts in the face of NULLs. = | F | T | N -

NULLs are built into the algebraic and arithmetic machinery of SQL. You can see how the equality operator (=) acts in the face of NULLs. = | F | T | N ---+---+---+--- F | 1 | 0 | ---+---+---+--- T | 0 | 1 | ---+---+---+--- N | | | Using the SELECT 1=NULL; syntax of SQLite we can see that SQLite does not even attempt to provide an answer. What would we say of something that cannot be determined? We say that it is _indeterminate_. So we can find out how NULLs behave by seeing what our database does (or reading the SQL spec.) But how we _interpret_ NULL is context and application specific. It's completely valid to interpret NULL as "data-is-missing" or "does-not-exist" if you so wish. Maybe the more reasonable interpretation is "unknown" as the article urges. However you have urged us to regard it (not the result of its operations which is another thing) as – at one and the same time – "the state does-not-exist", "zero", "irrelevant" which is unreasonable. Treating NULLs as unknowns and the results of operations on NULLs as indeterminate is a better recommendation I think even though ultimately the interpretation is application and context specific.