WITH
	Builder(line_n, word, word_position, amount)
AS
	(
	 SELECT
		line_n,
		'',
		0,
		MAX(word_position)
	 FROM
		table
	 GROUP BY
		line_n
	 UNION ALL
	 SELECT
		Data.line_n,
		CONCAT(Builder.word, CONCAT(' ', Data.word)),
		Data.word_position,
		Builder.amount
	 FROM
		Builder,
		table
	 WHERE
		table.line_n		= table.line_n
	   AND	table.word_position	= table.word_position + 1
	)
SELECT
	line_n,
	word
FROM
	Builder
WHERE
	word_position = amount;