Re: Real world issue:- OT recreational interval
Date: Tue, 19 Sep 2006 04:39:34 GMT
Message-ID: <awKPg.22750$9u.271240_at_ursa-nb00s0.nbnet.nb.ca>
JOG wrote:
> pamelafluente_at_libero.it wrote: >
>>kvnkrkptrck_at_gmail.com ha scritto:
>>
>>
>>>If it's not fear, then what is it? Pride? Lack of intelligence?
>>
>>
>>
>>I repeat this for the last time
>>==========================
>>
>>(1) Consider n=2, (n is the number of operands),
>> what is count distinct of { 3 , 3 } ?
It is the same as COUNT{3}
>>(2) Answer 1. Agree ? If yes proceed.
>>
>> So. Does Count Distinct satisfy this definition:
>>
>>(3) A binary function f ( x , y ) is called idempotent
>> if for all x ,
>> f ( x , x ) = x ?
Count distinct is a composition of two functions. Distinct projects onto a set of attributes. Count distinct then counts the result of the project. Count is not idempotent, but in this case it does not operate on any duplication. (Replication means something different in the database field.)
>>(4) count distinct of { 3 , 3 } = 1, which is different from 3.
>> It doesn't.
Using set notation: { 3, 3 } = { 3 } = { 3, 3, 3} = { 3, ... 3, 3} The count (cardinality) of the above set is 1 regardless how many times we repeat 3 in its representation. Received on Tue Sep 19 2006 - 06:39:34 CEST