| Outer joinsSuppose we have a database of Books and Authors. (Assume no books
have multiple authors.)
 Schema
create table Author(
    author_id int not null primary key,
    name varchar,
    birth_date date,
    birth_country varchar
);
create table Book(
    book_id int not null primary key,
    author_id int references Author,
    title varchar,
    year int
);
 |