创建视图语法：
CREATE [OR REPLACE] [FORCE|NOFORCE] VIEW view [(alias[, alias]...)] AS subquery [WITH CHECK OPTION [CONSTRAINT constraint]] [WITH READ ONLY [CONSTRAINT constraint]];
示例：
CREATE OR REPLACE VIEW empvu80 (id_number, name, sal, department_id) AS SELECT employee_id, first_name || ' ' || last_name, salary, department_id FROM employees WHERE department_id = 80;