Oracle 21c

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create table EMPLEADOS (CODIGO, NOMBRE) as
select 1, 'Alex' from dual union all
select 2, 'Ray' from dual
2 rows affected

create table TRABAJAN (COD_EMP, FUNCION) as
select 2, 'Development' from dual union all
select 3, 'Sales' from dual
2 rows affected

SELECT NOMBRE, FUNCION
FROM EMPLEADOS
JOIN TRABAJAN USING (CODIGO,COD_EMP);
ORA-00904: "EMPLEADOS"."COD_EMP": invalid identifier

SELECT NOMBRE, FUNCION
FROM (
  SELECT CODIGO AS COD_EMP, NOMBRE FROM EMPLEADOS
)
JOIN TRABAJAN USING (COD_EMP);


NOMBRE
FUNCION


Ray
Development


SELECT NOMBRE, FUNCION
FROM EMPLEADOS
JOIN TRABAJAN ON CODIGO = COD_EMP;


NOMBRE
FUNCION


Ray
Development