CREATE TABLE biographies (
    id SERIAL PRIMARY KEY,
    content TEXT NOT NULL
);

CREATE TABLE authors (
    id SERIAL PRIMARY KEY,
    name VARCHAR(100) NOT NULL,
    biography_id INT,
    FOREIGN KEY (biography_id) REFERENCES biographies(id)
);

CREATE TABLE books (
    ident SERIAL PRIMARY KEY,
    title VARCHAR(100) NOT NULL,
    author_id INT NOT NULL,
    FOREIGN KEY (author_id) REFERENCES authors(id) ON DELETE CASCADE
);

CREATE TABLE reviews (
    id SERIAL PRIMARY KEY,
    book_id INT NOT NULL,
    review TEXT NOT NULL,
    FOREIGN KEY (book_id) REFERENCES books(ident) ON DELETE CASCADE
);

CREATE TABLE genres (
    id SERIAL PRIMARY KEY,
    name VARCHAR(100) NOT NULL
);

CREATE TABLE book_genres (
    book_id INT NOT NULL,
    genre_id INT NOT NULL,
    PRIMARY KEY (book_id, genre_id),
    FOREIGN KEY (book_id) REFERENCES books(ident) ON DELETE CASCADE,
    FOREIGN KEY (genre_id) REFERENCES genres(id) ON DELETE CASCADE
);