Oracle 21c

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with 
function do_something(arg integer) return integer
is 
begin
    return arg+1;
end;
t as (SELECT 1 a FROM DUAL)
SELECT *
FROM   t
PIVOT  (
  ANY_VALUE(a+1)
  FOR a IN (1, 2)
);


1
2


2
null


with 
function do_something(arg integer) return integer
is 
begin
    return arg+1;
end;
t as (SELECT 1 a FROM DUAL)
SELECT *
FROM   t
PIVOT  (
  ANY_VALUE(do_something(a+1))
  FOR a IN (1, 2)
);


1
2


3
null


WITH 
function do_something(arg varchar2) return varchar2
is
begin
    return 'fff';
end;
t (a) AS (
  SELECT 'a' FROM DUAL UNION ALL
  SELECT 'b' FROM DUAL UNION ALL
  SELECT 'd' FROM DUAL
)
SELECT *
FROM   t
PIVOT (ANY_VALUE(do_something(a)) FOR a IN ('a', 'b', 'c', 'd'));


'a'
'b'
'c'
'd'


fff
fff
null
fff


WITH 
function do_something(
  arg varchar2
) return varchar2
is
begin
    return 'fff';
end;
t (a) AS (
  SELECT COLUMN_VALUE
  FROM   TABLE(SYS.ODCIVARCHAR2LIST('a', 'b', 'd'))
)
SELECT *
  FROM t PIVOT (ANY_VALUE(do_something(a)) FOR a IN ('a', 'b', 'c', 'd'));
ORA-22806: not an object or REF