11.1.1什么是视图 下一 employees employee_id(员IID) employee_name(员工姓名) employee position(员工职位) employee_age(员工年龄) employee_.address(员工住址) vw employee salary employee id(员工ID) 关系运算 salary employee name(员工姓名) month(月份) salary_id(工资ID) salary(工资) employee_.id(员IID) month(月份)】 salary(工资) currency(货币种类)salary salary_id (工资ID) employee_id (员工ID) month (月份) salary (工资) currency (货币种类) vw_employee_salary employee_id (员工ID) employee_name (员工姓名) month (月份) salary (工资) employees employee_id (员工ID) employee_name (员工姓名) employee_position (员工职位) employee_age (员工年龄) employee_address (员工住址) 关系运算