oracle按时间分组查询

• 按年查询：
  

  select count(*), to_char(column_name,'yyyy') from table_name group by  to_char(column_name,'yyyy');

• 按月查询：

        select count(*), to_char(column_name,''yyyy-mm'') from table_name group by to_char(column_name,''yyyy-mm'');

• 按周查询：

        select count(*), to_char(column_name,'iw') from table_name group by  to_char(column_name,'iw');