El uso de Alias ​​en la consulta da como resultado que el comando no finalice correctamente

Oracle no admite alias de tabla con as .

Por ejemplo:

SQL> select 1
  2  from dual as a;
from dual as a
             *
ERROR at line 2:
ORA-00933: SQL command not properly ended


SQL> select 1
  2  from dual a;

         1
----------
         1

De la misma manera:

SQL> select *
  2  from (
  3        select 1 from dual
  4       ) as a;
     ) as a
          *
ERROR at line 4:
ORA-00933: SQL command not properly ended


SQL> select *
  2  from (
  3        select 1 from dual
  4       )  a;

         1
----------
         1

El alias de columna puede tener y no tener as :

SQL> select 1 as one, 2 two
  2  from dual;

       ONE        TWO
---------- ----------
         1          2