On 2/9/12 5:25 PM, Rich Shepard wrote:
For water quality data the primary key is (site, date, param) since there's only one value for a given parameter collected at a specific site on a single day. No surrogate key needed.
Yea. I was wondering if the surrogate key debate really boils down to the composite primary key debate. Seems so in my mind, though one could maybe come up with a combination. Basically aliases of values and composite those. Perhaps that's the ultimate methodology. :)
The problem with real world data is that different taxonomic levels are used. Not all organisms can be identified to species; some (such as the round worms, or nematodes) are at the level of order. That means there is no combination of columns that are consistently not NULL. Sigh.
I didn't know that about worms. I did know grasses only went to the genus. You could make a tall skinny self referential table though, and nothing would be null and everything would be unique ( I think, unless certain taxon values can appear under different higher order taxon values ). Thanks for the view points out there. Cheers, -ds -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
