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

This may look archaic and overly simple, but it does not depend on window functions, CTE's and aggregating subqueries. In most cases it is also the fastest.

SELECT bk.id, au.id, au.name, bk.title as last_book
FROM author au
JOIN book bk ON bk.author_id = au.id
WHERE NOT EXISTS (
    SELECT *
    FROM book nx
    WHERE nx.author_id = bk.author_id
    AND nx.book_id > bk.book_id
    )
ORDER BY book.id ASC
    ;