Thanks Scott, Your comments are of worth.
I feel relatively clear with this concept and i stopped my mind as well from comparing inheritance concept with JAVA by saying that inheritance concept in humans, in JAVA and in Postgres is different in many aspects. I would like to share an example as well which describe the advantage of inheritance in Postgres in detail . Example can be found here<http://knol.google.com/k/postgresql-inheritance#> . On Wed, Dec 16, 2009 at 12:15 PM, Scott Marlowe <[email protected]>wrote: > On Wed, Dec 16, 2009 at 12:01 AM, ABBAS SHAKEEL > <[email protected]> wrote: > > Thanks Scott > > you are right . It inherits structure only and i don't know whether to > call > > to it an advantage or disadvantage that it query the children table as > well > > while select. But in case of insert and update this concepts takes a new > > turn. > > How inheritance effect data? > > Can you please briefly compare concept of inheritance in Postgres and > JAVA, > > as my mind is trying to compare this with already stored concept in mind > > about inheritance ;) > > I'm no Java specialist, so can't directly compare there. In the case > of inserts those go to the parent or, if you insert directly to them > the child tables. Updates operate on the appropriate child tables. > > By defining triggers or rules, you can make inserts to the parent > table go to appropriate child tables, which is often done for > partitioning data, which is in turn the most common use for table > inheritance. > > You can also select data from JUST the parent with the only keyword, > as in "select * from only parent_table". > > Note that pgsql supports multiple inheritance, so that you can have a > table inherit structure from two or more parent tables as well. > > Note that as of 8.4, according to the docs: > "All check constraints and not-null constraints on a parent table are > automatically inherited by its children. Other types of constraints > (unique, primary key, and foreign key constraints) are not inherited." > > So for foreign keys and such, inheritance is much less useful than > regular tables. > -- Best Regards Shakeel Abbas
