Hi, Tim,
I was looking for an opinion on the actual table structure. :-) How should i build the data set? Is my second example ok? The first is the long version but i wanted to put together all the common fields to both types of "sites" and then (maybe) build tables to accomodate the specific fields so there are no empty columns on the table if i put everything in the same table.
Pag
On Fri, Jul 9, 2010 at 10:30 AM, Tim Landscheidt <tim@xxxxxxxxxxxxxxxxxx> wrote:
Miguel Vaz <pagongski@xxxxxxxxx> wrote:
> [...]
> * sites (generic):You mean archaeological sites that are not also natural
> id_site
> name
> description
> x
> y
> * site_natural
> id
> id_site
> altitude
> * site_arqueology
> id
> id_site
> id_category
> id_period
> But i seem to be missing something. How can i have this in a way that its
> easy to list only "arqueology sites" for example. I feel the solution is
> simple enough, even for me, but its eluding me. Any help in the right
> direction would be very appreciated.
sites?
| SELECT * FROM site_arqeuology
| WHERE id_site NOT IN
| (SELECT id_site FROM site_natural);
There are numerous other ways to do this, i. e., with "LEFT
JOIN", "EXCEPT", etc.
Tim
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