connect by与with

相信很多人都用过connect by生成数值列表，如下所示

SQL> select level from dual connect by level <= 10;
     LEVEL
----------
         1
         2
         3
         4
         5
         6
         7
         8
         9
        10
10 rows selected

如果没有connect by或不让用connect by语句怎么办呢

可以试下with语句

SQL> with x(a) as
  2   (select 1 from dual union all select a + 1 from x where x.a < 10)
  3  select * from x;
         A
----------
         1
         2
         3
         4
         5
         6
         7
         8
         9
        10
10 rows selected