拆分字段中用逗号拼接的字段

业务，实验室负责人存的是用逗号拼接起来的用户ids,前台高级查询传过来用户的用户名

SELECT * FROM(
SELECT t.laboratory_id,
        t.dept_id,
        t.lab_name,
        t.lab_abb,
        t.manager_user_ids,
        t.telephone,
        t.status,
        t.location,
        t.scale,
        t.ask,
        t.content,
        t.create_user,
        t.create_date,
        t.update_user,
        t.update_date,
substring_index( substring_index( t.manager_user_ids, ',', b.help_topic_id + 1 ), ',',- 1 ) as manager_user_id
FROM base_laboratory t
JOIN mysql.help_topic b ON b.help_topic_id < ( length( t.manager_user_ids ) - length( REPLACE ( t.manager_user_ids, ',', '' ) ) + 1 ) 
) t 
LEFT JOIN sys_user su on t.manager_user_id = su.user_id
WHERE su.`name` like '%谭%'