Inheritance vs child tables (Was Domains)

On Fri, 1 Aug 2003, Ron Johnson wrote:

> On Fri, 2003-08-01 at 12:26, Francisco J Reyes wrote:
> > On Fri, 1 Aug 2003, Tom Lane wrote:
> [snip]
> > Currently I used inheritance to enforce the consitency
> > since a good number of fields needed to be common among the tables AND the
> > inheritted tables are basically a supperset of the data, so some times I
> > would want to access the inheritted tables and other times the parent/main
> > table.
>
> Isn't this when you'd really want child tables, instead?

I think both ways can accomplish the same (if not very simmilar
functionality), however I find using inherittance easier.
Not really sure about efficiency though.

A simple example of the type of design I am planning to do would be:

Table A
Userid
date entered
last changed

Table B inherited from A(additional fields)
person name
birthday

Table C inherited from A(additional fields)
book
isbn
comment

I plan to keep track of how many records a user has so with inherittance
it's easy to do this. I can count for the user in Table A and find out how
many records he/she has or I can count in each of the inheritted tables
and see how many there are for that particular table.

Inheritance makes it easier to see everything for a userid or just a
particular type of records.