per la cronaca, ho provato banalmente anche con un cast inutile nella query:
codice:
SELECT
book_id id,
title title,
author.author_id authorId,
author_name author,
editor.editor_id editorId,
editor_name editor,
CAST(price AS DECIMAL(6,2)) price,
isbn isbn,
note note,
scaffale scaffale
FROM book
INNER JOIN author ON author.author_id = book.author_id
INNER JOIN editor ON editor.editor_id = book.editor_id