Comment by setr

7 years ago

The article itself gives a pretty decent description of how the language falls down.. and the ggp’s expression of his impression pretty trivially just maps to the relational model/algebra.... so all necessary arguments have been made :-)

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setr

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marcus_holmes  7 years ago

really? the article has a handful of strange edge cases that you'll almost never smack into in practice, and that's cause to say the language is crap?

Given the vast usage of SQL and its overwhelming popularity, if there were real problems with the language then there would be a lot more noise about them. But most people seem to be happy with it.

If it's not broken, let's not fix it, eh?

  • setr  7 years ago

    The only edge cases I could find in the article were the discussion of nulls... which aren’t so much an edge case as they are just an ever-present problem that no one really notices until it hurts (its not at all difficult to write a broken-on-null query). Is there something else you’re referring to? Afaict, everything else was just trivially observable aspects of the language

    >Given the vast usage of SQL and its overwhelming popularity, if there were real problems with the language then there would be a lot more noise about them. But most people seem to be happy with it.

    In what universe does popularity imply quality? Certainly not the one I’m in — Avengers endgame is apparently #2 gross worldwide ever :-)

  • rbanffy  7 years ago

    There are real problems with COBOL and, yet, it's used in the most critical parts of our societal infrastructure. People just learned to live with the problems and are by now completely oblivious to them.

LoSboccacc  7 years ago

there's a reason why not everything in SQL is a set and it's that you can do a lot of mathematical work from inside the engines. this was largely overlooked in the article and undefined what operations between set of multiple cardinality would require and if this would result back to what they call unwieldy runtime errors when doing math over set of mismatched cardinality.

  • setr  7 years ago

    >there's a reason why not everything in SQL is a set and it's that you can do a lot of mathematical work from inside the engines

    I don’t see the relationship between those two things; or rather, what the latter even means. Can you expand?

    Also, apparently the “sets” described in the article are actually multisets aka bags [0] — so the same semantics as any other RDBMS/SQL. No idea why they’d confound the two, especially when set vs bag semantics is a well-discussed topic in the literature..

    [0] https://edgedb.com/docs/edgeql/overview/#everything-is-a-set

    • LoSboccacc  7 years ago

      something like this

      SELECT StudentID, Name, (SELECT COUNT(x) FROM StudentExam WHERE StudentExam.StudentID = Student.StudentID) / (SELECT COUNT(x) FROM StudentEnrollmetnPeriods WHERE StudentEnrollmetnPeriods.StudentID = Student.StudentID) AS ExamsTakenPerYear FROM Student ORDER BY ExamsTaken DESC;

      works because the result from aggregate are scalar and thus math operations always meaningful, albeit this in particular might not be the most brilliant example, there's definitely a case for running such operations on the server, because you might filter on the results, say, like

      "select all student with less than 2 exam per year average"

      at which point either you have the distinction between scalar and set in the language itself and you can filter invalid queries at the parsing level or you have to do the checks at runtime when two set are in an operation with mixed cardinality, halt the query and throw an error.

      edit: count(x) because I don't know how to escape asteriks

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