mysql字符串拆分

SELECT  SUBSTRING_INDEX(SUBSTRING_INDEX(a.path,\',\',b.help_topic_id + 1),\',\',-1) as path

FROM

(SELECT industrys as path FROM zc_project) a

JOIN 

mysql.help_topic b 

ON b.help_topic_id < (LENGTH(a.path)- LENGTH(REPLACE(a.path,\',\',\'\')) + 1);