mysql查询语句关联用户表，根据用户名转成用户姓名
select csi.information_id, csi.appeal_serial_number, csi.appeal_username, csi.accepter, csi.process_type, csi.process_source, csi.originate_date,act.ASSIGNEE_,
acu.name ,
csi.process_state from cs_information csi
left join act_ru_task act on csi.process_id = act.EXECUTION_ID_
left join ac_bureau_user acu on FIND_IN_SET(acu.user_name,act.ASSIGNEE_)
join cs_operated_detail cso on csi.information_id = cso.information_id
where 1 = 1 and csi.originator = 'administrator'
group by csi.appeal_serial_number
acu是用户表，asi是工单表，act是工作流表，
怎么写sql让name这一列显示对应的“姓名1，姓名2，姓名3”？