Hi, Antonello,
Antonello <
antonello.monetsen@...> wrote:
> I have a dilemma: is gid really useful in a geoDB?
> I am building a geodb for several harbor. When I create a layer(table
> with geometry) in postgis, I need a gid like a primary key, or I can use
> a different one? Can I use several field of from the table like a
> primary key?
> I am not new in the gis, but why in almost all geoDB I saw there is a
> gid?! Is it really necessary? Do it come from shapefile standards?
Technically, there's no need for a gid, from the database point of
view, as SQL deals with sets of rows.
However, most applications want some way of identifying specific rows,
especially when updating / editing data.
GID is generated by shp2pgsql.
> For example QuantumGIS doesn't work if the layer has only one primary
> key, there are other application that don't work like qGis?
QuantumGIS has the additional oddity that the primary key has to be of
type int4 - int8 or serial (which is optimal for primary keys) is not
accepted, AFAIK.
For read-only access, you can try MezoGIS which makes very little
assumptions about your database, and you can specify layers via
arbitrary queries.
Regards,
Markus
--
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf. | Software Development GIS
Fight against software patents in Europe! www.ffii.org
www.nosoftwarepatents.org
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