Message-ID: <45F0843D.5020407@Sheeky.Biz>
Date: Fri, 09 Mar 2007 08:16:37 +1030
From: Shane Ambler <pgsql@Sheeky.Biz>
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To: chester c young <chestercyoung@yahoo.com>
CC: sql pgsql <pgsql-sql@postgresql.org>,  greg.toombs@bluebottle.com
Subject: Re: inheritance
References: <437880.34674.qm@web54303.mail.yahoo.com>
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chester c young wrote:
>> --- Greg Toombs <greg.toombs@bluebottle.com> wrote:
>>
>>
>> I'm trying to figure out how to nicely implement a C++
> class-likesystem > > with PostgreSQL. Consider the following:
>> Tables Fruit, Apple, Orange
> 
> you can do this traditionally or through pg inheritance, although I do
> not think inheritance is well supported before 8.2.

Inheritance will most likely fit your C++ class-like system better and 
will not need foreign keys. Inheritance has been available in postgresql 
for many years and I think you will find it quite stable. (Not sure if 
pg6.x had it but it was available in 7.x) Historically a Table in 
postgresql was called a class (pre-sql) which is still reflected in the 
system catalogs with pg_class containing the list of tables and other 
classes like indexes....

http://www.postgresql.org/docs/8.2/interactive/ddl-inherit.html

You would then have table fruit as your base class and table oranges 
that inherits from fruit, giving it all the columns that fruit has plus 
any that are added to table oranges as well.

selecting from table fruit will allow you to get all rows from table 
apples and table oranges but not the columns unique to the apples or 
oranges tables.

Maybe then you'll add a table basket that has a foreign key to the fruit 
table....... ;-)


-- 

Shane Ambler
pgSQL@Sheeky.Biz

Get Sheeky @ http://Sheeky.Biz