select sum(count) as fcustcount
from (
         select ROW_NUMBER() over(partition by t1.channelid order by t1.time desc)as num,
                t1.count
         from tlive_usercount t1
                  inner join tlive t2 on t1.channelid = t2.channelid --and t2.livestatus='live'
     ) t
where t.num = 1