Re: Inheritance

Ian Turner wrote:
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> > `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

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