From: | Peter Eisentraut <peter(at)eisentraut(dot)org> |
---|---|
To: | watermelonmania79(at)gmail(dot)com, pgsql-docs(at)lists(dot)postgresql(dot)org |
Subject: | Re: 3.6 Inheritance Documentation |
Date: | 2023-08-08 09:36:40 |
Message-ID: | de8e9b34-0e9d-9fee-c9c5-bb2238c77c2a@eisentraut.org |
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Lists: | pgsql-docs |
On 02.08.23 21:54, PG Doc comments form wrote:
> In the provided example, the cities table and the capitals table have a
> parent-child relationship through inheritance. However, querying the cities
> table directly (e.g., SELECT name, elevation FROM cities WHERE elevation >
> 500;) will not automatically include data from the child table, capitals.
> Inheritance in PostgreSQL does not implicitly combine data from parent and
> child tables in a single query.
This observation is patently incorrect:
CREATE TABLE cities (
name text,
population real,
elevation int -- (in ft)
);
CREATE TABLE capitals (
state char(2) UNIQUE NOT NULL
) INHERITS (cities);
INSERT INTO cities (name) VALUES ('Ithaca');
INSERT INTO capitals (name, state) VALUES ('Albany', 'NY');
SELECT * FROM cities;
name | population | elevation
--------+------------+-----------
Ithaca | |
Albany | |
(2 rows)
SELECT * FROM capitals;
name | population | elevation | state
--------+------------+-----------+-------
Albany | | | NY
(1 row)
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