> If 3-value logic is such a good idea, why doesn't any modern general-purpose language use it? Many languages have a null/undefined of some sort, but they are

> If 3-value logic is such a good idea, why doesn't any modern general-purpose language use it? Many languages have a null/undefined of some sort, but they are often simply coerced to false. But, for a language whose sole purpose is to manipulate data the null value nearly always has meaning. > Given a SQL boolean expression `f(b)` that can return true, false, or null, how do I test if `f(b)` has returned NULL? How do I handle that NULL case? http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt Section 8.6, the null predicate. `where f(b) is null` > ANSI SQL gives users a strange new paradigm for boolean algebra and then says "GLHF" and gives you zero tools to handle the situation. It's also not a strange new paradigm, and is in fact built on foundational topics. Relational algebra and set theory are not new concepts.