在oracle树查询中加入其他表

SELECT employees.*
FROM employees
INNER JOIN departments ON employees.department_id = departments.department_id;

SELECT employees.*
FROM employees
LEFT JOIN departments ON employees.department_id = departments.department_id;

SELECT employees.*
FROM employees
RIGHT JOIN departments ON employees.department_id = departments.department_id;

SELECT
  employees.employee_id,
  employees.employee_name,
  departments.department_name
FROM employees
FULL OUTER JOIN departments ON employees.department_id = departments.department_id;

SELECT COUNT(*) as numberOfEmployees
FROM employees
WHERE department_id IN (
  SELECT department_id FROM departments
WHERE department_name = 'Marketing'
);

WITH employee_names (employee_name) AS (VALUES 'John Doe'),
     other_employees AS (SELECT * FROM employees)
SELECT e.employee_id, e.employee_name
FROM other_employees e
JOIN employee_names en ON e.employee_name = en.employee_name;