Re: primary key and uniqueness

On Fri, 23 Jun 2000, you wrote: > From: "Martin A. Marques" <martin@math.unl.edu.ar> > > > >Is it posible to create a table like this > > > >CREATE TABLE usuario ( > > U_id SERIAL PRIMARY KEY UNIQUE, > > U_nombre NCHAR(50), > >);> > I don't know. Is it? Have you tried it? What happened? Got an error! ;-) > >The question would be if I can combine "PRIMARY KEY" with "UNIQUE". Can I > >make any kind of combination of constraints? > > In this case PRIMARY KEY includes UNIQUE, so why would you want to? In fact, > this produces error 577 "this type of constraint already exists on this > column set". So, technically, the answer to your question is no. So with PRIMARY KEY I get it all! Do I get some other constraint? One last one. Is it posible to reference a field on a table to a field on another table that is not a PRIMARY KEY? Thanks!! -- "And I'm happy, because you make me feel good, about me." - Melvin Udall ----------------------------------------------------------------- Mart'n Marqu's email: martin@math.unl.edu.ar Santa Fe - Argentina http://math.unl.edu.ar/~martin/ Administrador de sistemas en math.unl.edu.ar -----------------------------------------------------------------