如何按时间段统计？

Question

select count(*) from tbname group by trunc(regtime);
select count(*) from tbname group by trunc(regtime,'mm');
select count(*) from tbname group by trunc(regtime,'yyyy');

Answer 1

我的意思是：
count(*)          month
--------------------------
  5               2003-11
  6               2003-12或：
  name            day
--------------------------
 张三            2004-01-01
 李四            2004-01-01
 王五            2004-01-02
 赵六            2004-01-02

Answer 2

select count(*),trunc(regtime) from tbname group by trunc(regtime);
select count(*),trunc(regtime,'mm') from tbname group by trunc(regtime,'mm');
select count(*),trunc(regtime,'yyyy') from tbname group by trunc(regtime,'yyyy');

Answer 3

select count(*),to_char(regtime,'yyyy-mm-dd hh24') from tbname group by to_char(regtime,'yyyymmddhh24')||decode(sign(to_char(regtime,'mi')-30),-1,'00','30');