如何在同一张表中复制记录

Question

现在我已经在这个问题上停留了很长时间，并取得了零进展。我甚至不知道是否有可能...

我有1台：

+------+------------+-------+---------+------------+ 
| Item | Date | RUnit | FDHUnit | Difference | 
+------+------------+-------+---------+------------+ 
| A | 19/04/2016 | 21000 | 20000 |  1000 | 
| B | 20/04/2016 | 2500 |  500 |  2000 | 
+------+------------+-------+---------+------------+ 

是否有可能为每个items的，这将显示创建在同一个表中的新行Difference，也许还有其他几列？

我所需的输出会是这样的：

+------+------------+-------+---------+------------+ 
| Item | Date | RUnit | FDHUnit | Difference | 
+------+------------+-------+---------+------------+ 
| A | 19/04/2016 | 21000 | 20000 |   | 
| A | 19/04/2016 | NULL | NULL |  1000 | 
| B | 20/04/2016 | 2500 | 500  |   | 
| B | 20/04/2016 | NULL | NULL |  2000 | 
+------+------------+-------+---------+------------+ 

原因是是，我想展现一个新列，并表明它要么是Held directly或not held directly。

Answer 1

是，使用union all：

select item, date, ruunit, fdhunit, difference 
from t 
union all 
select item, date, null, null, runit - fdhunit 
from t 
order by item, (case when runit is not null then 1 else 2 end); 

的order by结果放置的顺序，你的结果提示。没有order by，记录的排序是不确定的。

Answer 2

尝试这种方式

select * from 
(select item, date, ruunit, fdhunit, '' as difference 
from t 
union all 
select item, date, null as ruunit, null as fdhunit, difference 
from t) a 
order by item, date 

Answer 3

尝试这个

插入到表：

insert into table1 
select item,date,null,null,(Runit-fdhunit) from table1 where (Runit-fdhunit) 

正常结果： SELECT * FROM表1 UNION ALL 选择项目，日期，空， null，（Runit-fdhunit）from table1 where（Runit-fdhunit）<> 0

Answer 4

试试这个。更换cast(null as number)与实际类型difference列

select item, date, r.ruunit, r.fdhunit, r.difference 
from t 
cross apply ( 
    select n=1, ruunit, fdhunit, cast(null as number) difference 
    UNION 
    select n=2, null, null, difference) r 
order by item, date, n