SQL: Learning it the hard way

I'm current reading Learn SQL The Hard Way, It's the first book from "learncodethehardway" that I read. I really liked their teaching approach, they don't waste time, the entire book is really practical. If you want to learn some SQL, I suggest you to read THIS book.
Here is some basic SQL operations you'll learn in the beginning of the book:

Creating basic tables:

CREATE TABLE person (
  id INTEGER PRIMARY KEY,
  first_name TEXT,
  last_name TEXT,
  age INTEGER
);

CREATE TABLE pet (
  id INTEGER PRIMARY KEY,
  name TEXT,
  breed TEXT,
  age INTEGER,
  dead INTEGER
);

Creating a relation table between person and pet:

CREATE TABLE person_pet (
  person_id INTEGER,
  pet_id INTEGER
);

Inserting data:

INSERT INTO person (id, first_name, last_name, age) VALUES (0, 'bernardo', 'fire', 17);
INSERT INTO pet (id, name, breed, age, dead) VALUES (0, 'zeus', 'dog', 6, 0);

Inserting referential data:

INSERT INTO person_pet (person_id, pet_id) VALUES (0, 0);

Selecting Data:

SELECT * FROM person;
SELECT name, breed FROM pet;
SELECT name FROM pet WHERE breed = "unicorn";
SELECT * FROM pet WHERE dead = 0;

Select Across Many Table:

SELECT pet.id, pet.name, pet.age, pet.dead
    FROM pet, person_pet, person
    WHERE
    pet.id = person_pet.pet_id AND
    person_pet.person_id = person.id AND
    person.first_name = "bernardo";

Deleting Data:

DELETE FROM pet WHERE first_name = 'bernardo';

Droping table:

DROP TABLE person;

Deleting using other tables:

DELETE FROM pet WHERE id IN (
    SELECT pet.id
    FROM pet, person_pet, person
    WHERE
    pet.id = person_pet.pet_id AND
    person_pet.person_id = person.id AND
    person.first_name = "bernardo"
);

Removing the relation table since the pet doesn't longer exist.

DELETE FROM person_pet WHERE pet.id NOT IN (
    SELECT id FROM pet
);