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
Verifique
distinct on
Com distinct ativado é necessário incluir as colunas "distintas" na
order by . Se esse não for o pedido que você deseja, você precisa agrupar a consulta e 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
Outra solução é usar uma função de janela como na resposta de Lennart. E outra muito genérica é essa
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
