How to join only one row in joined table with postgres?

Question

I have the following schema:

CREATE TABLE author (
    id   integer
  , name varchar(255)
);
CREATE TABLE book (
    id        integer
  , author_id integer
  ,          


        

Answer 1

Here is one way:

SELECT book_id, author_id, author_name, last_book
FROM (
    SELECT b.id as book_id
         , a.id as author_id
         , a.name as author_name
         , b.title as last_book
         , row_number() over (partition by a.id
                              order by b.id desc) as rn
    FROM author a
    JOIN book b 
        ON b.author_id = a.id
) last_books
WHERE rn = 1;