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NOTE: use Perl; is on undef hiatus. You can read content, but you can't post it. More info will be forthcoming forthcomingly.

All the Perl that's Practical to Extract and Report

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  • My brain is hurting!

    Okay, not really. But this has been interesting reading.

    • What's really frustrating is that much of the problems associated with nulls would go away if database vendors would start supplying DBMS which enforce relational data (SQL doesn't). First, we would need something called "distributed foreign keys" -- mentioned in the PDF I link to. Next, databases would have to be optimized to handle 6NF, something which is rarely seen, and 1NF, something which is not well-understood. Further, queries would need to return relations. In other words, they would need to re

      • I can't believe I'm only now seeing this post...

        Since reading Database In Depth, I've also realized that the object-relational impedance mismatch is a myth. It is a persistent myth, but a myth none the less.

        Here's the quote from that book that I always go back to:

        All of which goes a long way, incidentally, toward explaining why a true "object/relational" system would be nothing more nor less than a true relational system—which is to say, a system that supports the relational model, with all that

  • Ovid,

    First of all, I don't understand how your example, perl -le 'print "yes" if (undef) < 4, is an example of three-value logic. The parentheses create a list, and a list in scalar context evaluates to the number of items it has, not the value of the first item.

    This works well because, unless I'm missing something, there is no three-value logic in Perl. Perl's undef is not the same as SQL's NULL; undef always evaluates to false! IOW, it is a value, just an undefined one.

    The easiest way f

    • A wise man (was it Perlis or Bentley or was he quoting?) once said the only sensible values for constants are 0 and 1, all else are parameters that may indeed change with requirements. (Two:=1+1 was allowed as a special case for buffer-swapping, one in use and one in prep. Perlis said something to the effect of any supposed constant is someone else's variable.)

      So Three-valued is probably a bad basis for a logic. Date's point about Nulls are there are many more one out-of-band value possible, and you rare

      --
      Bill
      # I had a sig when sigs were cool
      use Sig;