CREATE TABLE _authors (

  id MEDIUMINT(8) UNSIGNED AUTO_INCREMENT,

  name VARCHAR(100),

  some_field MEDIUMINT(8) UNSIGNED,

  PRIMARY KEY (id),

  index(some_field)

);

CREATE TABLE _books (

  id MEDIUMINT(8) UNSIGNED AUTO_INCREMENT,

  title VARCHAR(100),

  PRIMARY KEY (id)

);

CREATE TABLE _books2authors (

  author_id MEDIUMINT(8) DEFAULT 0,

  book_id MEDIUMINT(8) DEFAULT 0,

  index(author_id),

  index(book_id)

);

INSERT INTO _authors (name, some_field) VALUES 

('author1', 1),('author2', 2),('author3', 3);

INSERT INTO _books (title) VALUES 

('book1'),('book2'),('book3');

INSERT INTO _books2authors (author_id, book_id) VALUES 

(2,1),(3,2),(3,3);

SELECT 

	A.id, GROUP_CONCAT(B.title ORDER BY B.title DESC SEPARATOR ',') AS books, 0.1 + some_field AS having_field

FROM 

	_authors A

LEFT JOIN

	_books2authors B2A 

	FORCE INDEX(author_id) 

	ON B2A.author_id = A.id

LEFT JOIN 

	_books B ON B.id = B2A.book_id

WHERE 

	1

GROUP BY 

	A.id

HAVING 

	having_field < 2

ORDER BY

	having_field ASC

	;

DROP TABLE _authors, _books, _books2authors;