如何在同一張表中複製記錄

Question

現在我已經在這個問題上停留了很長時間，並取得了零進展。我甚至不知道是否有可能...

我有1臺：

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

是否有可能爲每個items的，這將顯示創建在同一個表中的新行Difference，也許還有其他幾列？

我所需的輸出會是這樣的：

+------+------------+-------+---------+------------+ 
| 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，我想展現一個新列，並表明它要麼是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結果放置的順序，你的結果提示。沒有order by，記錄的排序是不確定的。

Answer 2

嘗試這種方式

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

嘗試這個

插入到表：

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

正常結果： SELECT * FROM表1 UNION ALL 選擇項目，日期，空， null，（Runit-fdhunit）from table1 where（Runit-fdhunit）<> 0

Answer 4

試試這個。更換cast(null as number)與實際類型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