SUBSELECT na cláusula FROM

[Rafael_Santos]

Olá senhores,
estou estudando para OCA e resolvi dar uma olhada em subselects.
Realizei um subselect simples que retornou o seguinte erro:

ORA-00904: "DEP"."DEPARTMENT_ID": identificador inválido
00904. 00000 - "%s: invalid identifier"
*Cause:
*Action:
Erro na linha: 8 Coluna: 3

Estou utilizando o SQLDeveloper

A query utilizada segue:

Selecionar tudo

SELECT 
  dep.department_name, 
  emp.soma
FROM
  HR.departments,
  (SELECT department_id, SUM(salary) as soma FROM HR.employees GROUP BY department_id) emp
WHERE
  dep.department_id = emp.department_id;

[Rafael_Santos]

Resolvido, falatava o apelido da tabela departments.

Selecionar tudo

SELECT 
  dep.department_name, 
  emp.soma
FROM
  HR.departments dep,
  (SELECT department_id, SUM(salary) as soma FROM HR.employees GROUP BY department_id) emp
WHERE
  dep.department_id = emp.department_id;