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Date: Tue, 8 Aug 2023 11:36:40 +0200
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Subject: Re: 3.6 Inheritance Documentation
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To: watermelonmania79@gmail.com, pgsql-docs@lists.postgresql.org
References: <169100604868.635.1178692927881377748@wrigleys.postgresql.org>
From: Peter Eisentraut <peter@eisentraut.org>
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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)