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Relational algebra doesn't have nulls, but there's a difference between the mathematical theory and concepts and the reality of a relational system. As I menti
by da_chicken 8y ago
Relational algebra doesn't have nulls, but there's a difference between the mathematical theory and concepts and the reality of a relational system.
As I mention elsewhere, Codd's own list of rules for a relational database [0] explicitly require nulls (see Rule 3).
[0]: https://en.wikipedia.org/wiki/Codd%27s_12_rules https://en.wikipedia.org/wiki/Codd%27s_12_rules
- lmm 8y agoI don't see any entanglement with the rest of the rules, or with what makes a relational database a relational database. "A systemic way to represent missing and inapplicable information" may be necessary, but better alternatives to null are imaginable. A relational database without nulls sounds like an ML without exceptions: actually a pretty good idea.