> Is CREATE TYPE what you're looking for?
> http://www.postgresql.org/docs/8.0/static/sql-createtype.html
No. I'll try to give an exemple of what I want:
I suppose I have the following table
CREATE TABLE experiment (
distance DOUBLE,
time DOUBLE,
speed DOUBLE
);
I can do the following query :
SELECT distance+time+speed FROM experiment;
This is a valid SQL query, but there is no physical meaning.
Now, I suppose I have "extended type". So the table is:
CREATE TABLE experiment (
distance DOUBLE(m1),
time DOUBLE(s1),
speed DOUBLE(m1s-1),
);
distance is of type DOUBLE and of unit METER
time is of type DOUBLE and of unit SECOND
speed is of type DOUBLE and of unit METER/SECOND
SELECT distance+time+speed FROM experiment;
Would throw an error : "Incompatible unit M1, S1, M1S-1"
SELECT distance/time+speed FROM experiment;
would succeed (obviously).
It may be possible to mess with domain/type to achieve a draft.
But I pretty sure that we need extend the type system to achieve it
cleanly.
Cordialement,
Jean-Gérard Pailloncy
