По дням:
select convert(char(8),Date_and_Time,112) mydate, count(calls_id)
from calls
group by convert(char(8),Date_and_Time,112)
order by mydate
По месяцам:
select convert(char(6),Date_and_Time,112) mydate, count(calls_id)
from calls
group by convert(char(6),Date_and_Time,112)
order by mydate
По годам:
select convert(char(4),Date_and_Time,112) mydate, count(calls_id)
from calls
group by convert(char(4),Date_and_Time,112)
order by mydate