SELECT t1.art_number, GROUP_CONCAT( DISTINCT description_ru ) AS description_ru
FROM amortizators t1
INNER JOIN info_table_description td
INNER JOIN info_table_numbers_description tnd ON tnd.description_id = td.id
INNER JOIN info_table_numbers tn ON tn.id = tnd.numbers_id
JOIN info_table_numbers tn2 ON LOCATE( tn2.article_number, t1.search ) //это вообще не работает
WHERE t1.search LIKE  '%8245%'

SELECT  `description_ru` 
FROM  `info_table_description` td
INNER JOIN  `info_table_numbers_description` tnd ON tnd.description_id = td.id
INNER JOIN  `info_table_numbers` tn ON tn.id = tnd.numbers_id
WHERE  `article_number` =  '8245'

SELECT `art_number`, GROUP_CONCAT(DISTINCT description_ru) FROM `amortizators` 
JOIN (
SELECT  `description_ru` 
FROM  `info_table_description` td
INNER JOIN  `info_table_numbers_description` tnd ON tnd.description_id = td.id
INNER JOIN  `info_table_numbers` tn ON tn.id = tnd.numbers_id
WHERE  `article_number` =  '8245') as descr
WHERE `search` LIKE '8245%'

SELECT DISTINCT `art_number`, (
		SELECT  GROUP_CONCAT(DISTINCT `description_ru`) 
		FROM  `info_table_description` td
		INNER JOIN  `info_table_numbers_description` tnd ON tnd.description_id = td.id
		INNER JOIN  `info_table_numbers` tn ON tn.id = tnd.numbers_id
		WHERE  `amortizators`.`search` LIKE CONCAT('', `article_number` ,'%'))
FROM `amortizators` 
WHERE `search` LIKE '30%'