Re: Using a serial primary key as a foreign key in a second table

Thanks for the help Sean. You're right about the problem you
identified in my earlier reply concerning uniqueness, but fortunately
the problem is that I picked a bad example---in an attempt to distill
the essence of the problem I was was trying to solve from my own
messy database I oversimplified. What I'm trying to do is model
object inheritance in a relational database by defining 4 tables/
classes: 3 different types of children, each of which has its own
table, and a parent class that's represented by one table which
contains attributes common to all 3 child types. When I want to add
an "object", I add a row to one of the three child tables (depending
on the type of object I'm adding) and then add a record to the parent
class table...so a single object is represented by a row in two
different tables---I think it's called polymorphic association. I've
been struggling to concisely find a way to add the child entry
followed by the parent entry (which has to contain the ID of the child).

So thanks again, especially for the link to the "INSERT"
documentation. The line "If the INSERT command contains a RETURNING
clause, the result will be similar to that of a SELECT statement
containing the columns and values defined in the RETURNING list,
computed over the row(s) inserted by the command" seems to be new to
the 8.2 docs---and I've spent hours pouring over the 8.1.4 manual!

Nat


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