[mananaysiempre]

> What's the alternative, an empty string?

Yes! NULL is relational for “don’t know”, and SQL is (mostly, with varying degrees of success) designed to treat is as such. That’s why NULL=anything is NULL and not e.g. false (and IMO it’s a bit of a misfeature that queries that branch on a NULL don’t crash, although it’s still better than the IEEE 754 NaN=anything outright evaluating to false). If the value is funky but you do know it, then store a funky value, not NULL.

[TylerE]

But a known value of empty string is a fairly commonplace thing, and I have never wanted to treat that as null.

[mananaysiempre]

I’m not sure what to say here. ... Yes? If you’re referring to the Oracle behaviour where '' IS NULL, well, the rude way of putting it is that Oracle is doing a stupid. The more polite way of putting it is that Oracle is absolutely ancient and these parts probably existed long before people had the theory developed well enough to recognize which things make sense and which don’t, and now Oracle’s backward-compat-driven livelihood depends on not recognizing that it’s making no sense there. Either way, if this matters to you, you’re stuck and will have to work around this particular wart.