Re: Real world issue:- OT recreational interval
Date: 18 Sep 2006 17:38:45 -0700
Message-ID: <1158626325.582212.186770_at_d34g2000cwd.googlegroups.com>
pamelafluente_at_libero.it wrote:
>
> 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 ?
No, it does not satisfy the definition. count distinct, as understood in SQL, is not a binary function. It is an aggregate function. They are not the same. An aggregate function invoked on a relation of size two is not the same as a binary function.
> Tell me the precise statement which is wrong
> and prove that it is wrong. Show me your intelligence.
Statement 3 is wrong. It is not a question of proof, but rather a question of meeting a definition or not. Count distinct does not meet the definition.
Marshall Received on Tue Sep 19 2006 - 02:38:45 CEST