Oracle 11g Release 2

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
EXPLAIN PLAN FOR 
select value
from
(
    (
        select
            'a' v1,
            'b' v2
        from dual
    )
    unpivot
    (
        value
        for value_type in
            (v1,v2)
    )
);
select plan_table_output
from table(dbms_xplan.display('plan_table',null,'BASIC ROWS'));


PLAN_TABLE_OUTPUT


Plan hash value: 3882305214

 

-----------------------------------------

| Id  | Operation        | Name | Rows  |

-----------------------------------------

|   0 | SELECT STATEMENT |      |     2 |

|   1 |  VIEW            |      |     2 |

|   2 |   UNPIVOT        |      |       |

|   3 |    FAST DUAL     |      |     1 |

-----------------------------------------


EXPLAIN PLAN FOR 
select CASE WHEN uvp.flag = 1 THEN t.v1 WHEN uvp.flag = 2 THEN t.v2 ELSE NULL END value
from
(
    select
    'a' v1,
    'b' v2
    from dual
) t
CROSS JOIN
(
    SELECT 1 flag from dual
    UNION ALL
    SELECT 2 flag from dual
) uvp;
select plan_table_output
from table(dbms_xplan.display('plan_table',null,'BASIC ROWS'));


PLAN_TABLE_OUTPUT


Plan hash value: 2083928383

 

-----------------------------------------

| Id  | Operation        | Name | Rows  |

-----------------------------------------

|   0 | SELECT STATEMENT |      |     2 |

|   1 |  NESTED LOOPS    |      |     2 |

|   2 |   FAST DUAL      |      |     1 |

|   3 |   VIEW           |      |     2 |

|   4 |    UNION-ALL     |      |       |

|   5 |     FAST DUAL    |      |     1 |

|   6 |     FAST DUAL    |      |     1 |

-----------------------------------------