oracle:如何用sql生成日历

BI分析中，经常需要将事实表与时间维度表关联起来，按年/月/日来逐层展示，常用的做法是创建一张日历表，结构类似如下：

create table T_BAS_CALENDAR
(
  d_year  NUMBER(4) not null,
  d_month NUMBER(2) not null,
  d_day   NUMBER(2) not null
);
comment on table T_BAS_CALENDAR
  is '日历表';
comment on column T_BAS_CALENDAR.d_year
  is '年';
comment on column T_BAS_CALENDAR.d_month
  is '月';
comment on column T_BAS_CALENDAR.d_day
  is '日';
alter table T_BAS_CALENDAR
  add constraint PK_BAS_CALENDAR primary key (D_YEAR, D_MONTH, D_DAY);

但是如何向这张表批量插入日历数据，方法就很多了，下面是仅用SQL语言生成日历的参考方法：

 create or replace procedure P_IMPORT_CALENDAR(p_year_start number,
                                               p_year_end   number) is
   cmonth    integer;
   cyear     integer;
   cday      integer;
   day_first integer;
   day_last  integer;
 begin
   --生成从p_year_start到p_year_end的所有日历 created by yjmyzz@126.com 2015-04-27

   --firstly,delete history records
   delete from T_BAS_CALENDAR where d_year between p_year_start and p_year_end;
   for cyear in p_year_start .. p_year_end loop
     for cmonth in 1 .. 12 loop
       --get first-day of Month
       select to_number(cyear || lpad(cmonth, 2, '') || '', '')
         into day_first
         from dual;
       --last-day of Month
       select to_number(to_char(add_months(to_date(day_first, 'yyyyMMdd'), 1) - 1,
                                'yyyyMMdd'),
                        '')
         into day_last
         from dual;
       for cday in day_first .. day_last loop
         --insert to table
         INSERT INTO T_BAS_CALENDAR
           (D_YEAR, D_MONTH, D_DAY)
         VALUES
           (CYEAR, CMONTH, SUBSTR(cday, 7));
       end loop;
     end loop;
   end loop;
   commit;
 end P_IMPORT_CALENDAR;