复杂的观点

视图可以是非常复杂的查询（聚合，连接，子查询等）。只需确保为所选内容添加列名：

Create VIEW dept_income AS
SELECT d.Name as DepartmentName, sum(e.salary) as TotalSalary
FROM Employees e
JOIN Departments d on e.DepartmentId = d.id
GROUP BY d.Name;

现在你可以从任何表中选择它：

SELECT * 
FROM dept_income;