也许我误解了这个问题，但是-对我来说，它看起来像是3个选择的结合。
样本数据：

SQL> with test (colnum, col1, col2, col3) as
  2    (select 1, 'a', 'b', 'c' from dual union all
  3     select 2, 'x', 'y', 'z' from dual
  4    )

查询：

5  select colnum ||'-1-U' colnum, col1 col123
  6  from test
  7  union all
  8  select colnum ||'-2-U' colnum, col2
  9  from test
 10  union all
 11  select colnum ||'-3-U' colnum, col3
 12  from test
 13  order by 1;

COLNUM     COL123
---------- ----------
1-1-U      a
1-2-U      b
1-3-U      c
2-1-U      x
2-2-U      y
2-3-U      z

6 rows selected.

SQL>

你可以使用UNPIVOT子句：

SELECT colNum || '-' || col_code || '-U' as colNum, col123
FROM mytable
UNPIVOT(
    col123 
    FOR col_code
    IN (
        col1 AS '1', 
        col2 AS '2', 
        col3 AS '3'
    )
);

结果：

COLNUM  COL123
1-1-U   123
1-2-U   341
1-3-U   635
2-1-U   323
2-2-U   434
2-3-U   343

Demo here

你可以使用UNPIVOT和连接：

SELECT colNum || '-' || col || '-U' AS colNum,
       col123
FROM   table_name
       UNPIVOT(
         col123 FOR col IN (col1 AS 1, col2 AS 2, col3 AS 3)
       )

其中，对于样本数据：

CREATE TABLE table_name (colNum, Col1, Col2, Col3) AS
SELECT 1, 123, 341, 635 FROM DUAL UNION ALL
SELECT 2, 323, 434, 343 FROM DUAL;

输出：
| 栏目|COL123|
| --------------|--------------|
| 1-1-U|一百二十三|
| 1-2-U|三百四十一|
| 1-3-U|六三五|
| 2-1-U|三百二十三|
| 2-2-U|四三四|
| 2-3-U|三百四十三|
fiddle