Oracle将列显示为行

Question

如何通过后面的示例将多列转换为行编码？对于解决方案，我检查了许多样本，例如数据透视，解码等，但我没有达到绝对解决方案。

+---------+---------+---------+---------+
|  COL_1  |  COL_2  |  COL_3  |  COL_4  |
+---------+---------+---------+---------+

I wanna make columns like this;    

+---------+
|  COL_1  |
+---------+
|  COL_2  |
+---------+
|  COL_3  |
+---------+
|  COL_4  |
+---------+

Answer 1

也许你想要unpivot？

with demo as ( select 1 as col1, 2 as col2, 3 as col3, 4 as col4 from dual )
select * from demo
unpivot
( colvalue for col in (col1, col2, col3, col4) );

COL    COLVALUE
---- ----------
COL1          1
COL2          2
COL3          3
COL4          4

4 rows selected.