>
>
>-----Ursprüngliche Nachricht-----
>Von: RSmith [mailto:[email protected]]
>Gesendet: Freitag, 20. Dezember 2013 14:20
>An: General Discussion of SQLite Database
>Betreff: Re: [sqlite] Does not detect invalid column name when subexpression
>optimized away
>
>
>On 2013/12/20 14:09, Simon Slavin wrote:
>> On 20 Dec 2013, at 12:05pm, Dan Kennedy <[email protected]> wrote:
>>
>>> "1 OR unknown" is not unknown, it is 1. And so on. To summarize:
>>>
>>> sqlite> SELECT (0 AND NULL), (1 AND NULL), (0 OR NULL), (1 OR NULL);
>>> 0|null|null|1
>> Well if you're so smart,
>>
>> (A) Anything divided by itself is 1.
>> (B) Anything divided by zero is infinity.
>> (C) What is 0 / 0 ?
>>
>> There. That should keep you busy through the new year break.
>
>Heh - Sqlite fun threads for christmas!
>
>Of course A and B above are not the only mathematical rules in existence. 0 /
>0 is called indeterminate since there is no possible value x where ( x * 0 )
>=/= 0. Of course the >axiomatic equation:
> x * 0 = 0
>can be re-shuffled to show that:
> 0 = 0 / x
>when dividing by x both sides, but when dividing by 0 both sides it yields:
> 0 / 0 = x / 0
>which means x has to be zero for any value of x, which is itself contradictory
>and cannot ever be the case - and it also illuminates the reason why 0 / 0 =
>1 can never be assumed.
>
>What phased me more was the day my school teacher (eons ago) tried to explain
>why:
>x ^ 0 = 1 for any x...
>Personally I found this much harder to swallow than the indeterminate form of
>0/0. :)
>
>
>Well... that was the better part of 4 minutes... We'll need a few more
>conundrums to breach the new-years break, let's have it!
Sorry but algebraically it is not permissible to divide by zero. So your
transformation
x * 0 = 0
== divide by x =>
x * 0 / x --commutative multiplication-> 0 * x / x --(A)-> 0 * 1 --(original
equation)-> 0 = 0 / x
holds only for any x NOT EQUAL to zero
x * 0 = 0
== divide by zero (undefined operation) =>
x * 0 / 0 --(A)--> x * 1 -> x = inf <-(B)-- 0 / 0
--(B)--> x * inf -> inf = inf <-(B)-- 0 / 0
How come Ye to the expression 0 / 0 = x / 0? Not by dividing the axiom by zero,
but the unrelated 0 = x which is true for only one value of x...
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