inverse row to column

Question

I have a larger SQL that produces a similar output as this simplified example:

SELECT
  5 AS L0,
  2 AS L1,
  3 AS L2,
  4 AS L3
FROM DUAL

current output is this row:

| L0 | L1 | L2 | L3 |
|  5 |  2 |  3 |  4 |

desired output are this columns:

| kind | value |
|   0  |   5   |
|   1  |   2   |
|   2  |   3   |
|   3  |   4   |

I know I could get this by union the select 4 times. I'm looking for advice if union is the best I can do here and if this output can be achieved by other means.

I also found many examples to inverse a column to a row but here I'm looking for inversion from a row to column.

Answer 1

Please try UnPIVOT:

SELECT substr(kind,2,1) AS kind,"value" FROM 
(    
    SELECT
        5 AS l0,
        2 AS l1,
        3 AS l2,
        4 AS l3
    FROM dual
)temp unpivot include NULLS ("value" FOR kind IN (l0, l1 , l2, l3));

Inversely:

 SELECT *   
 FROM 
 (
      SELECT Kind,
             max(Value) Value
      FROM table 
      GROUP BY Kind
 ) PIVOT ( max(Value) FOR Kind IN (L0, L1, L2, L3) );

Assuming that you actually have a table to query from.

Answer 2

select i - 1 kind,

    case when i = 1 then L0
         when i = 2 then L1
         when i = 3 then L2
         when i = 4 then L3
     end  as value
  from your_table,
       (select level as i from dual connect by level <= 4)

This does a Carteasan Product of your table and the "inline view." The inline view will output four rows, 1 through 4.