7 ms·

QUEL ( https://en.wikipedia.org/wiki/QUEL_query_languages https://en.wikipedia.org/wiki/QUEL_query_languages ), the original query-language for Ingres, was more

QUEL ( https://en.wikipedia.org/wiki/QUEL_query_languages https://en.wikipedia.org/wiki/QUEL_query_languages ), the original query-language for Ingres, was more orthogonal and consistent than SQL. But IBM decided SQL was more business friendly. Who can argue with that. And before that there was ALPHA. From https://www.labouseur.com/courses/db/s2-Remembering-Codd-2.pdf https://www.labouseur.com/courses/db/s2-Remembering-Codd-2.p... : "Ted [Codd] also saw the potential of using predicate logic as a foundation for a database language. He discussed this possibility briefly in his 1969 and 1970 papers, and then, using the predicate logic idea as a basis, went on to describe in detail what was probably the very first relational language to be defined, Data Sublanguage ALPHA, in “A Data Base Sublanguage Founded on the Relational Calculus,” Proc. 1971 ACM SIGFIDET Workshop on Data Description, Access and Control, San Diego, Calif. (November 1971). ALPHA as such was never implemented, but it was extremely influential on certain other languages that were, including in particular the Ingres language QUEL and (to a lesser extent) SQL as well."

nealabq 6y ago
Ted Codd designed the Relational Calculus as a clean relational-query language. It looks mathematical (scary?) and a little like a set-comprehension. But I think the big mistake is its use of non-ascii chars like ∃ ∈ ∀. Here's an example from http://arwan.lecture.ub.ac.id/files/2013/10/4.-relationalcalculus.pdf http://arwan.lecture.ub.ac.id/files/2013/10/4.-relationalcal... : SQL: SELECT DISTINCT F.Name FROM FACULTY F WHERE NOT EXISTS (SELECT * FROM CLASS C WHERE F.Id=C.InstructorId AND C.Year=2002) Relational Calculus: {F.Name | FACULTY( F) AND NOT (∃C ∈ CLASS( F.Id=C.InstructorId AND C.Year=2002))}
- anyfoo 6y ago
  I only had a quick look, is it a computer-friendly offshoot of relational algebra[1], the actual mathematical model for relational databases, as an actual query language? [1]https://en.wikipedia.org/wiki/Relational_algebra https://en.wikipedia.org/wiki/Relational_algebra
  - kd5bjo 6y ago
    Relational calculus is another mathematical model that is dual to relational algebra: if you have one representation you can always get the other. Relational algebra describes a fairly direct set of manipulations of database rows that can be implemented efficiently. Relational calculus operations are more abstract, but have useful identity transformations you can use to optimize query plans. So, when you ask a database system to perform a query, you ask it in relational algebra terms because they’re easy to understand. It then transforms your query into a relational calculus-like form to shuffle things around, and then back to a different, but equivalent, algebraic form to actually execute.
    - anyfoo 6y ago
      Thank you, that makes perfect sense.
  - garmaine 6y ago
    Relational algebra is functional programming: you map-reduce your way to a solution set. Relational calculus is logical programming: you specify what the solution looks like and the query engine figures out the sequence of operations to find a solution.
    - anyfoo 6y ago
      A useful analogy indeed, thanks.
      - garmaine 6y ago
        It goes a bit deeper than an analogy, but regardless I’m glad it helped! EDIT: To explain, the relational algebra IS a map-reduce functional programming language. The relational calculus IS a logical programming language. They just use tuples and sets instead of the more familiar lists and strings of LISP, Forth, Prolog, etc. And the sibling comment further up is right to point out that there are mechanical transformations to turn one into the other, just like there are automatic ways to compile Prolog into LISP (and vice-versa, though that is rarely done).
- xiaodai 6y ago
  ∃ ∈ ∀. quite natural to me as a pure math grad there exists, in, for all
  - nealabq 6y ago
    It's a mistake if your goal is to have the language implemented and become popular. Otherwise I like the notation. Computer languages would be different if Ascii had provided code points for ∧ ∨ ∩ ∪ ≡ ↑ etc. It's too bad so much real estate is wasted in the control chars.
    - kps 6y ago
      \ was invented so that ∧ and ∨ could be written /\ and \/. In retrospect, a mistake. Original ASCII (1963) had ↑, but it was converted to ^ in 1967 so that it could double as a circumflex. (Also ←, which was a good assignment operator; it's too bad _ didn't replace \ instead.)
  - krick 6y ago
    You don't even need to be a math grad for it to be natural. It's just a natural way to perform set operations, pretty much everybody who knows a little bit of math is familiar with it. End even if you are not, you need like 5-10 minutes to learn it, and then maybe a couple of weeks of using it to become really fluent. And I feel like "is not ASCII" is pretty silly complaint in 2020 anyways. First of, if these characters would be widely used in 1980, they would be on every keyboard today, same as it was on keyboards for APL. Second, you don't really have them to be literally ∀ and ∃, it could have been &A and &E for example, and then every other IDE, including some fancy product of JetBrains, vim & emacs and most likely even your mysql-cli (at least some wrapper around it written in Python) would turn them into pretty ∀ and ∃ on your screen, same as some editors do for λ. And third, which is a personal pet peeve of mine (so I probably should keep my mouth shut about that, but I cannot): I really, really wish we'd stop with all this ASCII bullshit already. There's nothing special about ASCII except it's 7-bit. And that's outdated. It may come as a shock to your average American, but most of the texts in the world are not ASCII, just deal with it. If your product doesn't support that, it probably means it's broken, outdated and will eventually lose to a competition, so you don't do yourself a favour forgetting about that. And with regards to input, there's nothing complicated about typing ∀ (or anything else like that) on an ordinary US-layout keyboard. For me ∀ is 3 very fluent keystrokes. I use XCompose, which is a blessing, but other operating systems have similar software with similar capabilities as well. I understand that this is not something most people are familiar with, but that's just bad and shouldn't be respected: using a mouse also wasn't familiar to every single PC-user out there. With demand comes the supply. So I really dream about the day when typing nice, clear syntax like ∀ instead of awkward Perl-like character sequences (to read which you need mentally traumatizing professional deformation and/or an IDE post-processor) becomes the norm of programming.

nealabq 6y ago

Ted Codd designed the Relational Calculus as a clean relational-query language. It looks mathematical (scary?) and a little like a set-comprehension. But I think the big mistake is its use of non-ascii chars like ∃ ∈ ∀. Here's an example from http://arwan.lecture.ub.ac.id/files/2013/10/4.-relationalcalculus.pdf http://arwan.lecture.ub.ac.id/files/2013/10/4.-relationalcal... : SQL: SELECT DISTINCT F.Name FROM FACULTY F WHERE NOT EXISTS (SELECT * FROM CLASS C WHERE F.Id=C.InstructorId AND C.Year=2002) Relational Calculus: {F.Name | FACULTY( F) AND NOT (∃C ∈ CLASS( F.Id=C.InstructorId AND C.Year=2002))}

anyfoo 6y ago
I only had a quick look, is it a computer-friendly offshoot of relational algebra[1], the actual mathematical model for relational databases, as an actual query language? [1]https://en.wikipedia.org/wiki/Relational_algebra https://en.wikipedia.org/wiki/Relational_algebra
- kd5bjo 6y ago
  Relational calculus is another mathematical model that is dual to relational algebra: if you have one representation you can always get the other. Relational algebra describes a fairly direct set of manipulations of database rows that can be implemented efficiently. Relational calculus operations are more abstract, but have useful identity transformations you can use to optimize query plans. So, when you ask a database system to perform a query, you ask it in relational algebra terms because they’re easy to understand. It then transforms your query into a relational calculus-like form to shuffle things around, and then back to a different, but equivalent, algebraic form to actually execute.
  - anyfoo 6y ago
    Thank you, that makes perfect sense.
- garmaine 6y ago
  Relational algebra is functional programming: you map-reduce your way to a solution set. Relational calculus is logical programming: you specify what the solution looks like and the query engine figures out the sequence of operations to find a solution.
  - anyfoo 6y ago
    A useful analogy indeed, thanks.
    - garmaine 6y ago
      It goes a bit deeper than an analogy, but regardless I’m glad it helped! EDIT: To explain, the relational algebra IS a map-reduce functional programming language. The relational calculus IS a logical programming language. They just use tuples and sets instead of the more familiar lists and strings of LISP, Forth, Prolog, etc. And the sibling comment further up is right to point out that there are mechanical transformations to turn one into the other, just like there are automatic ways to compile Prolog into LISP (and vice-versa, though that is rarely done).
xiaodai 6y ago
∃ ∈ ∀. quite natural to me as a pure math grad there exists, in, for all
- nealabq 6y ago
  It's a mistake if your goal is to have the language implemented and become popular. Otherwise I like the notation. Computer languages would be different if Ascii had provided code points for ∧ ∨ ∩ ∪ ≡ ↑ etc. It's too bad so much real estate is wasted in the control chars.
  - kps 6y ago
    \ was invented so that ∧ and ∨ could be written /\ and \/. In retrospect, a mistake. Original ASCII (1963) had ↑, but it was converted to ^ in 1967 so that it could double as a circumflex. (Also ←, which was a good assignment operator; it's too bad _ didn't replace \ instead.)
- krick 6y ago
  You don't even need to be a math grad for it to be natural. It's just a natural way to perform set operations, pretty much everybody who knows a little bit of math is familiar with it. End even if you are not, you need like 5-10 minutes to learn it, and then maybe a couple of weeks of using it to become really fluent. And I feel like "is not ASCII" is pretty silly complaint in 2020 anyways. First of, if these characters would be widely used in 1980, they would be on every keyboard today, same as it was on keyboards for APL. Second, you don't really have them to be literally ∀ and ∃, it could have been &A and &E for example, and then every other IDE, including some fancy product of JetBrains, vim & emacs and most likely even your mysql-cli (at least some wrapper around it written in Python) would turn them into pretty ∀ and ∃ on your screen, same as some editors do for λ. And third, which is a personal pet peeve of mine (so I probably should keep my mouth shut about that, but I cannot): I really, really wish we'd stop with all this ASCII bullshit already. There's nothing special about ASCII except it's 7-bit. And that's outdated. It may come as a shock to your average American, but most of the texts in the world are not ASCII, just deal with it. If your product doesn't support that, it probably means it's broken, outdated and will eventually lose to a competition, so you don't do yourself a favour forgetting about that. And with regards to input, there's nothing complicated about typing ∀ (or anything else like that) on an ordinary US-layout keyboard. For me ∀ is 3 very fluent keystrokes. I use XCompose, which is a blessing, but other operating systems have similar software with similar capabilities as well. I understand that this is not something most people are familiar with, but that's just bad and shouldn't be respected: using a mouse also wasn't familiar to every single PC-user out there. With demand comes the supply. So I really dream about the day when typing nice, clear syntax like ∀ instead of awkward Perl-like character sequences (to read which you need mentally traumatizing professional deformation and/or an IDE post-processor) becomes the norm of programming.