how to auto increment primary key in oracle code example

Example 1: oracle auto_increment

-- Use a sequence:
CREATE SEQUENCE id_seq START WITH 1;
INSERT INTO my_table (ID, VALUE) VALUES (id_seq.NEXTVAL, 'My value');

Example 2: oracle create auto increment column

CREATE TABLE animals (
     id MEDIUMINT NOT NULL AUTO_INCREMENT,
     name CHAR(30) NOT NULL,
     PRIMARY KEY (id)
);

INSERT INTO animals (name) VALUES
    ('dog'),('cat'),('penguin'),
    ('lax'),('whale'),('ostrich');

SELECT * FROM animals;
+----+---------+
| id | name    |
+----+---------+
|  1 | dog     |
|  2 | cat     |
|  3 | penguin |
|  4 | lax     |
|  5 | whale   |
|  6 | ostrich |
+----+---------+