mysql-MySQL中的group_concat函数怎么用sybase实现？

select distinct a.computername,a.mac , GROUP_CONCAT(distinct a.username) as usernames,GROUP_CONCAT(distinct a.userid) as userids from (select distinct nons.* , users.username,client.computername from noncontrol_softwares nons left join users on nons.userid=users.userid left join client on nons.mac=client.mac) as a group by a.mac

怎么将这段MySQL语句转换成sybase的？