Re: Inheritance

Ian Turner wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> > `SELECT * FROM Entities*;'
> >
> > up to and including 7.0.x.
> >
> > In 7.1, I believe a select on the parent will automatically show the
> > children and you will need to do something like `SELECT * FROM ONLY Entities'
> > to exclude descendant tables.
>
> Yes, but what about referential integrity? Can I have a table column
> reference a column from Entities*? In my experimentation, this is not the
> case.

Referential integrity doesn't work with inheritance, and will
not in 7.1.

It isn't possible to put a unique constraint on a column of
Entities* (AFAIK). So that a SELECT pkey FROM Entities will
never return any duplicates? The RI implementation of
PostgreSQL doesn't insist on such a unique constraint to
exist up to now, but it is required by the SQL specs and thus
we'll do so someday.

pgsql=# create table t1 (pkey integer primary key);
NOTICE: CREATE TABLE/PRIMARY KEY will create implicit index 't1_pkey' for table 't1'
CREATE
pgsql=# create table t2 (val integer) inherits (t1);
CREATE
pgsql=# insert into t1 values (1);
INSERT 21274 1
pgsql=# insert into t2 values (1, 11);
INSERT 21275 1
pgsql=# select * from t1;
pkey
------
1
1
(2 rows)

Am I missing something here?

Jan

--

#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
# Let's break this rule - forgive me. #
#================================================== JanWieck(at)Yahoo(dot)com #