How to create table using oracle database

Question

Good evening I am a beginner in the Oracle database I wanted to create 3 tables as follows if you can explain to me please.

Architecture of my database:

Answer 1

Use an Object Table:

CREATE TYPE country IS OBJECT (
  country_name VARCHAR2(100)
) NOT FINAL;

CREATE TYPE city UNDER country (
  city_name VARCHAR2(100)
) NOT FINAL;

CREATE TYPE capitol UNDER city (
  area VARCHAR2(100)
);

CREATE TABLE countries OF country;
CREATE TABLE cities OF city;
CREATE TABLE capitols OF capitol;

Then you can insert like this:

INSERT INTO capitols ( country_name, city_name, area )
VALUES ( 'Country', 'City', 'Area' );

and the capitols table has inherited the columns from its ancestor type.

db<>fiddle