contar registros

No agrupes por el campo agent

select datepart(hour,start_time) as hora ,count(agent) as agente
from easy..ag_in_cp_log 
where campaign='64' 
and convert(varchar(10),start_time,103)='04/05/2013' 
and datepart(hour,start_time)='4' 
group by datepart(hour,start_time)

Sergio Sánchez Arias
AYÚDANOS A AYUDARTE