Split comma seperated values and concatenate with other row values in MYSQL
SELECT DISTINCT CONCAT(SUBSTRING_INDEX(SUBSTRING_INDEX(numbers,',',num),',',-1),'_sub_',id) results
FROM `table`, (SELECT 1 num UNION ALL
               SELECT 2     UNION ALL
               SELECT 3     UNION ALL
               SELECT 4) nums


The numbers count in nums subquery is to be equal or greater than max values count in CSV field. If values count is fixed and numbers count is equal to it, you may remove DISTINCT.

If MySQL version is 8+, the numbers pseudotable can be generated in CTE.