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SQL nulls are weird

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Re: SQL nulls are weird

#191

Post by Pxtl »

gigatexal wrote: post #124
hiAndrewQuinn wrote: post #27

SQL NULLs aren't weird , they're just based off of Kleene's TRUE-FALSE-UNKNOWN logic! If you want you can read NULL as UNKNOWN and suddenly a whole bunch of operations involving them become a lot more intuitive: 1. TRUE OR UNKNOWN = TRUE, because you know you have at least one TRUE already. 2. TRUE AND UNKNOWN = UNKNOWN, because you don't know whether you have two TRUEs or not. It's just out there. 3. UNKNOWN XOR UNK…

This is the correct way of thinking about things. Null is one of the hardest things for traditional software engineers in my experience as a guy who came up as a data admin.

> Null is one of the hardest things for traditional software engineers

Making them harder is not better.

Re: SQL nulls are weird

#192

Post by Pxtl »

tessierashpool9 wrote: post #134
hiAndrewQuinn wrote: post #27

SQL NULLs aren't weird , they're just based off of Kleene's TRUE-FALSE-UNKNOWN logic! If you want you can read NULL as UNKNOWN and suddenly a whole bunch of operations involving them become a lot more intuitive: 1. TRUE OR UNKNOWN = TRUE, because you know you have at least one TRUE already. 2. TRUE AND UNKNOWN = UNKNOWN, because you don't know whether you have two TRUEs or not. It's just out there. 3. UNKNOWN XOR UNK…

there is a pattern starting to emerge here on hackernews of highly voted posts by people who present themselves as experts and thought leaders who shamelessly put their lack of understanding at display. it's frightening.

Or maybe people understand but still think it's dumb and hideously inconvenient?

Ergonomics matter.

Re: SQL nulls are weird

#193

Post by bunderbunder »

zie wrote: post #180
tessierashpool9 wrote: post #144

Earlier quoted context omitted.

go the extra mile and click on about and then check out the linkedin profile. i quote: "I graduated top of my class with a BSc in Computer Science [...]. I have a strong background in software engineering and technical leadership"

Who doesn't think of themselves as an expert? That doesn't mean they are one.

Why not both? In my career, I have met countless people who are experts in programming in general, but with relatively modest skills in database systems.

Which is fine! It's really hard to be truly expert in both. There's a reason why "programmer" and "database administrator" used to be two different professions. I'd like to think that I'm better than your average developer at flogging RDBMSes, but most DBAs I've worked with can still run circles around me when it comes to information modeling and database & query optimization.

Re: SQL nulls are weird

#194

Post by Pxtl »

thayne wrote: post #85
hiAndrewQuinn wrote: post #27

SQL NULLs aren't weird , they're just based off of Kleene's TRUE-FALSE-UNKNOWN logic! If you want you can read NULL as UNKNOWN and suddenly a whole bunch of operations involving them become a lot more intuitive: 1. TRUE OR UNKNOWN = TRUE, because you know you have at least one TRUE already. 2. TRUE AND UNKNOWN = UNKNOWN, because you don't know whether you have two TRUEs or not. It's just out there. 3. UNKNOWN XOR UNK…

If only it had a name that was more indicative of that, like UNKNOWN, or UNDEFINED or INDERTIMINATE or something.

Honestly, at this point I just wish SQL servers supported proper discriminated union types and nullable columns were implemented as some kind of MaybeKnown and I could just have a normal Maybe with normal equality semantics if I wanted.

SQL needs to join 21st century type systems... or needs to get replaced altogether. SQL is the FORTRAN of relational programming languages, but hangs around because every time somebody tries to replace it they throw the relational-theory baby out with the bath-water.

Re: SQL nulls are weird

#195

Post by taco_emoji »

zzzeek wrote: post #170
fauigerzigerk wrote: post #159

Earlier quoted context omitted.

>They shouldn't be hiding SQL from your primary language, they should be exposing the relational model to it! But this has never been their primary purpose and it's not what they are good at. ORMs are supposed to map the relational model into an object oriented model so that you can work with objects rather than sets of tuples. And that's exactly how people use them. ORMs incentivise people to replace simple and decl…

> ORMs are just a terrible idea - conceptually messy, hard to debug and optimise, full of needless complexity. and that's why ORMs are so unpopular and entirely absent from successful production applications for the past 30 years

yeah I mean, isn't all of this true for ANY abstraction? Once you're off the beaten path, they're all hard to debug and optimize, they introduce extra complexity, etc. BECAUSE they are attempting to abstract away certain details

This is true for an HTTP library as much as it is an ORM.

Re: SQL nulls are weird

#196

Post by marcosdumay »

masklinn wrote: post #42
layer8 wrote: post #29

Earlier quoted context omitted.

SQL NULL doesn’t behave like “unknown” in all contexts. That’s one issue of NULL, that it doesn’t really have consistent semantics.

Furthermore if null only means unknown then we need a value for “known absent”, there’s a reason why null is so often used as that.

We could really use some kind of "polymorphic table" that can represent a sum type in a convenient way.

Re: SQL nulls are weird

#197

Post by marcosdumay »

throwaway10235 wrote: post #21
demurgos wrote: post #15

Earlier quoted context omitted.

The main pain point for smaller apps is that every major Postgres version requires an explicit migration of the underlying data representation. I get why it's there, but for simpler apps I would appreciate a flag to do it transparently.

I'm not sure what you mean. I have migrated versions without having to update any applications that connects to it? Maybe it is a driver specific issue? I have used Python/Java, and haven't updated any of my code or dependencies because of a major Postgre update

The GP is complaining about the need to run the upgrade cluster command, and reconfigure your server when you want to use a different version of postgres itself. MySql does it transparently if you just open the database in the new server.

Of course, lots of people also think it's a feature. But those aren't very vocal. Anyway, this is a main reason why people keep using old postgres versions, they have to think about upgrading, and they often don't.

Re: SQL nulls are weird

#198

Post by cm2187 »

bballer wrote: post #158
cm2187 wrote: post #116

Earlier quoted context omitted.

The problem is that in practice in a database NULL is a placeholder for a missing value, not an unknown value.

And to further apply semantics to this just to be snide, the value is only "missing" if it could possibly ever be defined for that tuple. There are cases where you expect the value to be "missing", and it not being "missing" would be considered a data integrity issue. Fun.

Yes I should have rather written “an absence of data”. But still not “unknown”.

Re: SQL nulls are weird

#199

Post by gigatexal »

drpossum wrote: post #138
gigatexal wrote: post #124

Earlier quoted context omitted.

This is the correct way of thinking about things. Null is one of the hardest things for traditional software engineers in my experience as a guy who came up as a data admin.

Null in not-SQL (which is most things) usually isn't this tortured and isn't hard.

Yeah the 3 valued logic of SQL trips people up, me too from time to time

Re: SQL nulls are weird

#200

Post by gigatexal »

Pxtl wrote: post #191
gigatexal wrote: post #124

Earlier quoted context omitted.

This is the correct way of thinking about things. Null is one of the hardest things for traditional software engineers in my experience as a guy who came up as a data admin.

> Null is one of the hardest things for traditional software engineers Making them harder is not better.

Never said it was
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