ORACLE

CREATE OR REPLACE VIEW VISTA1 AS
SELECT employee_id, first_name, last_name
FROM employees;

CREATE OR REPLACE VIEW VISTA2 AS
SELECT employee_id, first_name, last_name
FROM employees
WHERE salary >= 5000;

CREATE OR REPLACE VIEW VISTA3 AS
SELECT employee_id, first_name, last_name
FROM employees
WHERE manager_id IS NULL;

CREATE OR REPLACE VIEW VISTA4 AS
SELECT e.employee_id, e.first_name, e.last_name, d.department_id, d.department_name
FROM employees e join departments d
ON e.department_id = d.department_id
WHERE e.department_id IN (10,30,50);

CREATE OR REPLACE VIEW VISTA5 AS
SELECT employee_id, first_name, last_name, TO_CHAR(hire_date, 'DD') || ' de ' ||TO_CHAR(hire_date, 'MONTH') || ' del año ' || TO_CHAR(hire_date, 'YYYY') AS fecha
FROM employees;