Re: Nearest Common Ancestor Report (XDb1's $1000 Challenge)

On 26 May 2004 11:48:55 -0700, Neo wrote:

>> > In XDb1's db, 'john isa thing' is not stored because it can be derived.
>> > Since 'isa' is transitive 'john isa thing' is derived
>> > form 'john isa person' and 'person isa thing'.
>>
>> In my database, 'john isa thing' is not stored either, because it can be
>> derived. Everything is a thing.
>
>Show me a method to determine person's class with the provided
>solution and I will show you how it will fail if the data is changed
>(ie the name of thing is changed from 'thing' to 'thingy' or
>'object'). This failure will not occur with XDb1.

(Based on original implementation)

SELECT     things.thing, classes.class
FROM       things
LEFT  JOIN classes
      ON   classes.thing = things.thing
WHERE      things.thing = 'john'

(Based on second implementation)

SELECT     things.thingName, classes.className
FROM       things
LEFT  JOIN ClassOfThings
      ON   ClassOfThings.thing = things.thing
INNER JOIN classes
      ON   classes.class = ClassOfThings.class
WHERE      things.thingName = 'john'

Best, Hugo

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