On Tue, 2007-03-20 at 10:21 -0400, Merlin Moncure wrote: > On 3/19/07, Elena <elena.planas@xxxxxxxxx> wrote: > > Hello all, I'm new in PostgreSQL... > > > > I would want to know like PostgreSQL manages the type reference that defines > > the standard SQL:1999. I want to define the type of attribute like a > > reference at other type. > > > > For example, in Oracle8i the definition is: > > > > -- Type Department > > CREATE OR REPLACE TYPE Department_type AS OBJECT ( > > code NUMBER(5), > > name VARCHAR(40) > > ); > > > > -- Type Employee > > CREATE OR REPLACE TYPE Employee_type AS OBJECT ( > > code NUMBER(5), > > name VARCHAR2(40), > > department REF Department_type -- Reference to Department object type > > ); > > > > how is this different from simply nesting the types? > Nesting the types would prevent other tuples from containing a reference to the same tuple of Department_type. I don't think a reference is the best thing to do here. A foreign key fits the relational model much better, and really has no disadvantage that I can see. What can a reference do that a foreign key can't? Regards, Jeff Davis
