On Tue, 2007-03-20 at 10:21 -0400, Merlin Moncure wrote:
> On 3/19/07, Elena <[EMAIL PROTECTED]> 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
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