Re: modeling either/or relationship...

Murdoc wrote:
> Essentially, the end result for the proposed 'hierarchical' design is a nightmare:
>
> Vehicle
> SUV
> 4-Door
> 2-Door
> SED
> 4-Door
> 2-Door
> STW (Station Wagon)
> HTC (Hatchback)
> TRK (Truck)
> SMI (Semi-Trailer)
> RDT (Road Train)
> UTE
>
> The list would be endless.

Could you expand on why would this be a nightmare?

The only thing that strikes me with the hierarchical class structure as posted by Celko is that I am not clear about how I would go about querying it (but perhaps this is due to limitations in my SQL skills).

Perhaps someone in the now could put me on the right track - If I did want to know (for example) how many 4-door cars there were in the system my impression is that I would not be able to extract this information this in a single SQ: query (I would insted use some sort of external script processing to process query results before firing off new ones), as somehow I will have to be matching entries in the Vehicle table (e.g. the Char(3) SUV) to other actual table names, before I query those tables to count their rows? Received on Wed Feb 01 2006 - 01:08:21 CET