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Comment by coldtea | Hacker News Reader

>Honestly, if it were not for Venn diagrams, I may have never learned how SQL joins work. It might not be perfect, but if you'd tried to make 16-year-old me understand relational algebra in order to grok how the joins in his Django site were working, he'd have given up before he began.

The whole point of the article is that there are different visualizations that are much better than Venn diagrams (in fact Venn diagrams are totally misleading), and they don't require any relational algebra.

That said, if someone doesn't know what a cartesian product is (high school level math), perhaps they shouldn't be allowed near a database...

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>if someone doesn't know what a cartesian product is (high school level math), perhaps they shouldn't be allowed near a database...

This is such an intellectually snobbish position to take. I can tell you that I didn’t know this term when I first interacted with a database, and if someone had told me the above, I would have just felt stupid and given up.

The fact you learned what a Cartesian product was at high school shouldn’t preclude someone who hasn’t from trying to build stuff and experiment with tech. Not everyone learns things the same way, or in the same order, and that’s okay.

>This is such an intellectually snobbish position to take.

Intellectually snobbish is "everyone should listen to Mahler and read Epictetus in the original language".

This is just basic professional requirement...

>The fact you learned what a Cartesian product was at high school shouldn’t preclude someone who hasn’t from trying to build stuff and experiment with tech.

Just not in any capacity where people depend on their output...

You didn't say "should not be allowed near a production database" you said "database"

That is very different. This was a 16 year old kid trying to mess around and learn stuff, he should be able to be around databases all he wants. I wouldn't hire him as a DBA, but he should be able to learn without having to wait for more advanced math.

>You didn't say "should not be allowed near a production database" you said "database". That is very different.

And that's what I meantt, so since you agree that's "that's very different", we're on the same page.

>a 16 year old kid trying to mess around and learn stuff, he should be able to be around databases all he wants

Well, it's not like a comment on HN is going to stop them.

Well, you were replying to someone who said they learned SQL for their Django site when they were 16, and you admonished them for not knowing Cartesian products and using a database... so it was certainly not clear that you meant a production database.

So now databases should be restricted to professional environments?

No, but people responding to comments should be restricted to using the Principle of Charity:

https://en.wikipedia.org/wiki/Principle_of_charity

You should be charitable to the creators of venn diagrams and the countless and diverse group of people who've found them useful for years. For instance, it obviously stands to reason that these sort of visual cheat-sheets are aimed primarily at novices, not experienced/professional DBAs.

Should we critique "lefty loosey righty tighty" because a professional mechanic knows that's not precisely true and should be able to analyze the context of the screw to determine whether it's left or right handed? Of course not, that mnemonic is for novices, not professional mechanics.

> if someone doesn't know what a cartesian product is (high school level math), perhaps they shouldn't be allowed near a database

Knowing what is meant when a term or symbol is used is not math, it's language.

You can know the meanings of all kinds of terms and symbols, and you will still not know anything about math, you'll only know something about mathematicians and how they like to communicate.

Conversely, someone may understand the math perfectly well but not know the correct terms or symbols (perhaps they learned under a different system, in a different country, etc.)

>Knowing what is meant when a term or symbol is used is not math, it's language.

When the symbol is a mathematical symbol, and describes a mathematical operation, then "knowing what is meant" by it means you know a piece of math.

Besides I wasn't describing what you "know" if you know what a Cartesian Product is. I was stating (as a fact) where you learn it (at high school math classes).

A person can know the integral sign and know vaguely that it means "the area under a curve" without actually knowing calculus. Understanding the semantics of a term or symbol and being familiar with its referent are very different things. This is universally accepted and not controversial at all. If you'd like to continue arguing your point, I'd ask you to provide even a modicum of evidence.

In terms of what you're "stating (as a fact)," I can tell you with absolute certainty that you're wrong. Many high schools do not teach set theory and, among those that do, many - mine included - don't refer to this operation as the Cartesian product. It is simply "the product of A x B."

> I was stating (as a fact) where you learn it (at high school math classes).

Interestingly your "fact" is false - from my experience. You'd need to specific country where this high school is located, the year of the syllabus and possibly a region within a country. When I went to "high school" (we don't call it that) the syllabus differed by region.

And we never studied cartesian products.

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