Esclareça como encontrar a junção externa direita e esquerda corretamente com um exemplo
Vou tentar mostrar a diferença entre a sintaxe de junção externa do Oracle e a Sintaxe ANSI/ISO .
LEFT OUTER JOIN -
SELECT e.last_name,
d.department_name
FROM employees e,
departments d
WHERE e.department_id = d.department_id(+);
SELECT e.last_name,
d.department_name
FROM employees e
LEFT OUTER JOIN departments d
ON (e.department_id = d.department_id);
RIGHT OUTER JOIN -
SELECT e.last_name,
d.department_name
FROM employees e,
departments d
WHERE e.department_id(+) = d.department_id;
SELECT e.last_name,
d.department_name
FROM employees e
RIGHT OUTER JOIN departments d
ON (e.department_id = d.department_id);
JUNÇÃO EXTERNA COMPLETA -
Antes do suporte nativo de hash full outerjoin em 11gR1, o Oracle converteria internamente o FULL OUTER JOIN da seguinte maneira -
SELECT e.last_name,
d.department_name
FROM employees e,
departments d
WHERE e.department_id = d.department_id(+)
UNION ALL
SELECT NULL,
d.department_name
FROM departments d
WHERE NOT EXISTS
(SELECT 1 FROM employees e WHERE e.department_id = d.department_id
);
SELECT e.last_name,
d.department_name
FROM employees e
FULL OUTER JOIN departments d
ON (e.department_id = d.department_id);
Veja isso.