Oracle实现POSTGRESQL的generate_series功能

PostgreSQL 有生成序列的函数，能够方便的进行造数据。这里我用ORACLE实现了PGSQL的generate_series函数功能。
POSTGRESQL.

t_girl=# select * from generate_series(1,10);
 generate_series
-----------------
               1
               2
               3
               4
               5
               6
               7
               8
               9
              10
(10 行记录)

时间：1.290 ms
t_girl=# select * from generate_series(1,10,2);
 generate_series
-----------------
               1
               3
               5
               7
               9
(5 行记录)

时间：0.431 ms
t_girl=# select * from generate_series(1,10,3);
 generate_series
-----------------
               1
               4
               7
              10
(4 行记录)

时间：0.879 ms
t_girl=# select * from generate_series(2,10,3);
 generate_series
-----------------
               2
               5
               8
(3 行记录)

时间：0.867 ms

t_girl=# select count(*) from generate_series(1,1000);
 count
-------
  1000
(1 行记录)

时间：1.142 ms

t_girl=# select to_char(now() - ‘1 day‘::interval * n,‘YYYY-MM-DD‘) as result from generate_series(1,10)  g(n);
   result
------------
 2015-12-08
 2015-12-07
 2015-12-06
 2015-12-05
 2015-12-04
 2015-12-03
 2015-12-02
 2015-12-01
 2015-11-30
 2015-11-29
(10 行记录)

时间：17.284 ms

ORACLE：

12:10:34 SQL> select * from table(ytt_generate_series(1,10));

COLUMN_VALUE
------------
           1
           2
           3
           4
           5
           6
           7
           8
           9
          10                                                                    

已选择 10 行。

已用时间:  00: 00: 00.02
12:10:36 SQL> select * from table(ytt_generate_series(1,10,2));

COLUMN_VALUE
------------
           1
           3
           5
           7
           9                                                                    

已用时间:  00: 00: 00.00
12:10:54 SQL> select * from table(ytt_generate_series(1,10,3));

COLUMN_VALUE
------------
           1
           4
           7
          10                                                                    

已用时间:  00: 00: 00.00
12:10:56 SQL> select * from table(ytt_generate_series(2,10,3));

COLUMN_VALUE
------------
           2
           5
           8                                                                    

已用时间:  00: 00: 00.02
12:11:04 SQL> select count(*) from table(ytt_generate_series(1,1000));

  COUNT(*)
----------
      1000                                                                      

已用时间:  00: 00: 00.13

13:32:13 SQL> select to_char(sysdate - n,‘YYYY-MM-DD‘) from table(ytt_generate_series(1,10));

TO_CHAR(SY
----------
2015-12-08
2015-12-07
2015-12-06
2015-12-05
2015-12-04
2015-12-03
2015-12-02
2015-12-01
2015-11-30
2015-11-29

已选择 10 行。

已用时间:  00: 00: 00.01

附上代码:

-- Declare result set.
create or replace type ytt_num is object
( n number);
/
create or replace type numbers_table is table of ytt_num;
/
-- Function body.
-- Created by ytt.
-- 2015/12/9
create or replace function ytt_generate_series
(
f_start_num number := 1, -- Start number.
f_end_num number,  -- Finish number.
f_step_num number := 1 -- Step.
)
return numbers_table pipelined
is
  list numbers_table := numbers_table();
  i number := 0;
  j number := 1;
begin
  i := f_start_num;
  j := 1;
  -- Increase nested table‘s size.
  list.extend(f_end_num);
  -- Loop begin.
  while i <= f_end_num loop
  -- Initlization.
    list(j) := ytt_num(null);
    list(j).n := i;
    pipe row(list(j));
    i := i + f_step_num;
    j := j + 1;
  end loop;
  return;
end;
/