PostgreSQL Database is an ORDBMS. An RDBMS that implements object-oriented features such as user-defined types, inheritance, and polymorphism is called an object-relational database management system (ORDBMS).
PostgreSQL implements inheritance between tables (or, if you like, between classes). Functions and operators are polymorphic.
Example.,
Function overloading
| Function with a single argument | Function with two argument |
|
CREATE OR REPLACE FUNCTION sum_fn(sum INTEGER) |
CREATE OR REPLACE FUNCTION sum_fn(sum INTEGER,sum2 INTEGER) RETURNS INTEGER AS $$ DECLARE result INTEGER; BEGIN result=sum*sum2; RETURN result; END; $$ LANGUAGE plpgsql; |
| postgres=# select sum_fn(21); sum_fn ——– 31 |
postgres=# select sum_fn(21,21); sum_fn ——– 441 |
Operator overloading
select x,
1 + x as “1+”,
‘127.0.0.1’::inet + x as “ip address”,
date ‘today’ + x as date
from (values (0), (1), (2), (3)) as t(x);
Output
x | 1+ | ip address | date
–+—-+————+————
0 | 1 | 127.0.0.1 | 2020-03-01
1 | 2 | 127.0.0.2 | 2020-03-02
2 | 3 | 127.0.0.3 | 2020-03-03
3 | 4 | 127.0.0.4 | 2020-03-04
(4 rows)
Here, the operator(+), is overloaded based on the value like integer, inet and date etc
Inheritance
PostgreSQL implements inheritance between tables in the following way.
create table logs_q1
(check (created_at >= date ‘2014-01-01’ and created_at <= date ‘2014-03-31’))
inherits (logs);
where logs in the parent table and logs_q1 is the child table.
Everything is Object in PostgreSQL, your table is identified by OID (Object ID), your user, tablespace, schema, everything is Object here.
Hence your PostgreSQL is considered as ODBMS.