Re: A new proof of the superiority of set oriented approaches: numerical/time serie linear interpolation

"Cimode" <cimode_at_hotmail.com> wrote in message news:1177873628.360842.277700_at_u30g2000hsc.googlegroups.com... [snip]

> I can not say I disagree with what you are saying but I still think
> you are missing the point of the example.
>
> As a practionner who used intensively both procedural and set based
> methods, on may manage to get response time to be faster using cursors
> (that still need s to be established) but that does not mean that
> performance as a whole is improved.
>
> Self joins poor implementations is a known direct image systems
> limitation. That is the issue I was trying to underline here.
> Discussing tuning on a specific SQL DBMS implementation is not the
> point of the thread nor the point of the NG. THe main point here is
> to see if linear interpolation could be a way of handling
> systematically missing numeric/datetime data...
>

I think that self-joins would be problematic regardless of the implementation. They are necessary only when dependencies exist between tuples within the same relation. It's like using a single relation for graphs instead of one relation for verticies and a separate relation for edges. It can be done, but should it?

On to your main point: Are you suggesting that the schema definition for a temporal relation include some form of "active" default definition, wherein a scalar expression would be stored in lieu of a value? Or maybe not stored, but evaluated whenever a missing value is accessed? Sounds like an interesting idea. I think the semantics would require some form of second-order logic, however.

[snip] Received on Sun Apr 29 2007 - 23:01:39 CEST