select语句中的重复行

Question

例如，我有两行

id|amount
 1|4
 2|1

如何复制超过1的行？

1|1
1|1
1|1
1|1
2|1

Answer 1

使用connect by：

可以轻松实现

with sample_data as (select 1 id, 4 amount from dual union all
                     select 2 id, 1 amount from dual)
select id, 1
from   sample_data
connect by prior id = id
           and prior dbms_random.value is not null
           and level <= amount;

        ID          1
---------- ----------
         1          1
         1          1
         1          1
         1          1
         2          1