with tmp1 as 

(select datetime,ci,(TCH_Erlang) as 最忙话务量,(TCH_Erlang/(0.1+Available_Tch_Mean)) as erlpertch,

Customer_Tch_Block_Rate,Available_Tch_Mean,(counter_1278093417) as 配置载频数,

(counter_1278093418) as 可用载频数目,ROW_NUMBER () over (partition by [CI] order by [TCH_Erlang] DESC) as 话务排序

from dbo.PH201704_Center_CELL

where datetime>='2017-4-28')

select tmp1.*

from tmp1

where 话务排序=1