select distinct on (author.id)
book.id, author.id, author.name, book.title as last_book
from
author
inner join
book on book.author_id = author.id
order by author.id, book.id desc
Compruebe distinct on
Con distinto activado es necesario incluir las columnas "distintas" en el order by
. Si ese no es el orden que desea, debe ajustar la consulta y reordenar
select
*
from (
select distinct on (author.id)
book.id, author.id, author.name, book.title as last_book
from
author
inner join
book on book.author_id = author.id
order by author.id, book.id desc
) authors_with_first_book
order by authors_with_first_book.name
Otra solución es usar una función de ventana como en la respuesta de Lennart. Y otra muy genérica es esta
select
book.id, author.id, author.name, book.title as last_book
from
book
inner join
(
select author.id as author_id, max(book.id) as book_id
from
author
inner join
book on author.id = book.author_id
group by author.id
) s
on s.book_id = book.id
inner join
author on book.author_id = author.id