mysql 把某列由变成行 mysql 一列变多行

mysql一行转多行、根据指定字符分割，还能看到分割成了几份

SELECT
	substring_index(
		substring_index(
			`a`.`executor`,
			',',(
				`b`.`help_topic_id` + 1 
			)),
		',',-(
			1 
		)) AS `coop_branch`,
	substr( `a`.`dispatch_list_datetime`, 1, 4 ) AS `dyear`,
	substr( `a`.`dispatch_list_datetime`, 6, 2 ) AS `dmonth`,((
			length( `a`.`executor` ) - length(
			REPLACE ( `a`.`executor`, ',', '' ))) + 1 
	) AS `executor_count`,
	a.*
FROM
	(
		`emp_cas`.`bm_dispatch_list` `a`
	JOIN `mysql`.`help_topic` `b` ON ((
	`b`.`help_topic_id` < (( length( `a`.`executor` ) - length( REPLACE ( `a`.`executor`, ',', '' ))) + 1 ))))