6 ms·

There is an argument that if your data does not have natural keys -- that if it depends on the addition of arbitrary system IDs to prevent duplication -- then i

by dghf 9y ago

There is an argument that if your data does not have natural keys -- that if it depends on the addition of arbitrary system IDs to prevent duplication -- then it is not truly relational.

ScottBurson 9y ago
Interesting that you would say that. It does seem to me that if your rows have these arbitrary IDs, they are more like objects than relational purists would like to admit. (I seem to recall that the relational people used to beat up on OODBs for lacking this relational purity. But OODBs are pretty much dead anyway, I guess.)
- theoh 9y ago
  But, to state the obvious, anonymous items in computing (e.g. anonymous functions, or untitled/unaddressed draft emails etc.) generally need to be assigned an id for the software to keep track. The practice of avoiding natural keys and assigning unique ids is analogous. No paradigm is implied.
  - TeMPOraL 9y ago
    In programs, anonymous objects always have an unique ID automatically assigned - by the very virtue of being separate entities. Usually those IDs are what we call "references" in programming.
    - theoh 9y ago
      I'm talking about the level of e.g. programming language implementation. A lambda needs to be assigned an id, for example, but it's not a reference that the user can manipulate. It's an implementation detail, as are surrogate keys.
      - TeMPOraL 9y ago
        You don't manipulate the reference directly (i.e. you shouldn't learn its numeric value (though you can - useful for debugging), and you can't change it) - but you do use it indirectly all the times with ==, eq, or however the referential equality operator is called in a given programming language. This is what, given (excuse the Java): MyObject a = new String("choo choo"); MyObject b = a; MyObject c = new String("choo choo"); allows you to observe that: a == b; a != c; b != c; even though: a.equals(b); a.equals(c); b.equals(c); under string comparison. This is exactly like surrogate keys. An implementation detail that's crucial to the meaning of the whole thing.
- TeMPOraL 9y ago
  Interesting indeed. I'd say that a primary thing that makes an object is its identity - and the identity is never a part of object data, nor it could ever be. In programming languages, objects' basic identities are determined by however the language implements references; in databases, a natural solution would be a surrogate unique key...
  - int_19h 9y ago
    That's exactly it. And furthermore, objects in real world also have identities, which are distinct from their attributes. You aren't you because you have a certain name and date of birth, or a certain SSN. You're you because you're you. And we all intuitively know and understand this concept of identity. So any software that deals with real world entities has to reflect that concept, which is exactly what synthetic primary keys do. And it might not be purely relational; but if purely relational model cannot handle this, then it's simply not a particularly useful model for most practical scenarios. BTW, a pedantic argument could be made here that, ultimately, identity of physical objects is also data - you just need to go low-level enough (ultimately, the identity of any entity is its wavefunction) to see that. Of course, that ignores the practical aspects.
    - Koshkin 9y ago
      > You're you because you're you. Are you sure that 'you' today is the same as 'you' yesterday? The notion of identity, however intuitive it may seem to some, is far from being universally obvious.
      - int_19h 9y ago
        It's universally obvious in a sense that every human culture and every human language has it (or at least I'm not aware of examples of the contrary). And it may well be fuzzy, but it's rather telling that this fuzziness nevertheless remains confined to philosophy and metaphysics. Asharites, for example, believed that the world is recreated by God "at every moment" (and that this is what makes the notions of time, motion etc possible), so in that sense, every person is also re-created. But their societies did not derive any peculiar social customs from that belief - they still treated any person at any given moment as if they possessed stable identity over time in practice.
awj 9y ago
Sure, and I can see that, but my argument is that natural keys which depend on business logic are subject to definitions that can change given a long enough time frame.

by dghf 9y ago

There is an argument that if your data does not have natural keys -- that if it depends on the addition of arbitrary system IDs to prevent duplication -- then it is not truly relational.

ScottBurson 9y ago

Interesting that you would say that. It does seem to me that if your rows have these arbitrary IDs, they are more like objects than relational purists would like to admit. (I seem to recall that the relational people used to beat up on OODBs for lacking this relational purity. But OODBs are pretty much dead anyway, I guess.)

theoh 9y ago
But, to state the obvious, anonymous items in computing (e.g. anonymous functions, or untitled/unaddressed draft emails etc.) generally need to be assigned an id for the software to keep track. The practice of avoiding natural keys and assigning unique ids is analogous. No paradigm is implied.
- TeMPOraL 9y ago
  In programs, anonymous objects always have an unique ID automatically assigned - by the very virtue of being separate entities. Usually those IDs are what we call "references" in programming.
  - theoh 9y ago
    I'm talking about the level of e.g. programming language implementation. A lambda needs to be assigned an id, for example, but it's not a reference that the user can manipulate. It's an implementation detail, as are surrogate keys.
    - TeMPOraL 9y ago
      You don't manipulate the reference directly (i.e. you shouldn't learn its numeric value (though you can - useful for debugging), and you can't change it) - but you do use it indirectly all the times with ==, eq, or however the referential equality operator is called in a given programming language. This is what, given (excuse the Java): MyObject a = new String("choo choo"); MyObject b = a; MyObject c = new String("choo choo"); allows you to observe that: a == b; a != c; b != c; even though: a.equals(b); a.equals(c); b.equals(c); under string comparison. This is exactly like surrogate keys. An implementation detail that's crucial to the meaning of the whole thing.
TeMPOraL 9y ago
Interesting indeed. I'd say that a primary thing that makes an object is its identity - and the identity is never a part of object data, nor it could ever be. In programming languages, objects' basic identities are determined by however the language implements references; in databases, a natural solution would be a surrogate unique key...
- int_19h 9y ago
  That's exactly it. And furthermore, objects in real world also have identities, which are distinct from their attributes. You aren't you because you have a certain name and date of birth, or a certain SSN. You're you because you're you. And we all intuitively know and understand this concept of identity. So any software that deals with real world entities has to reflect that concept, which is exactly what synthetic primary keys do. And it might not be purely relational; but if purely relational model cannot handle this, then it's simply not a particularly useful model for most practical scenarios. BTW, a pedantic argument could be made here that, ultimately, identity of physical objects is also data - you just need to go low-level enough (ultimately, the identity of any entity is its wavefunction) to see that. Of course, that ignores the practical aspects.
  - Koshkin 9y ago
    > You're you because you're you. Are you sure that 'you' today is the same as 'you' yesterday? The notion of identity, however intuitive it may seem to some, is far from being universally obvious.
    - int_19h 9y ago
      It's universally obvious in a sense that every human culture and every human language has it (or at least I'm not aware of examples of the contrary). And it may well be fuzzy, but it's rather telling that this fuzziness nevertheless remains confined to philosophy and metaphysics. Asharites, for example, believed that the world is recreated by God "at every moment" (and that this is what makes the notions of time, motion etc possible), so in that sense, every person is also re-created. But their societies did not derive any peculiar social customs from that belief - they still treated any person at any given moment as if they possessed stable identity over time in practice.

awj 9y ago

Sure, and I can see that, but my argument is that natural keys which depend on business logic are subject to definitions that can change given a long enough time frame.