oracle 与ms sql对日期字段使用group by

oracle 与ms sql对日期字段使用group by
oracle:
select to_char(date_time,'yyyymmdd'),count(*) from table_name where ……
group by to_char(date_time,'yyyymmdd')
order by to_char(date_time,'yyyymmdd')
或
select trunc(date_time),count(*)
from table_name
where .......
group by trunc(date_time)
ms sql：
SELECT SUM(field_name) FROM table_name GROUP BY month(date_time)
--上面这句只和月份有关，与年份无关
或
SELECT SUM(field_name) FROM table_name GROUP BY CONVERT(char(10),date_time,121)