定义：视图在数据库中只是一种逻辑存在。它们可作用表，但是数据视图可以包括连接，聚集和过滤器。

语法：CREATE VIEW <view name> AS <selete statement>

优点：对表进行筛选；节省硬盘控件；过滤内容

案例：CREATE VIEW Employees_vw  AS  SELECT EmployeeID,FirstName,MiddleInitial,LastName,Title,HireDate,TerminationDate,ManagerEmpID,Department  FROM  Employees;

案例：

CREATE VIEW CurrentEmployees_vw
AS
SELECT EmployeeID,FirstName,MiddleInitial,LastName,Title,HireDate,ManagerEmpID,Department FROM Employees WHERE TerminationDate IS NULL;

DATEADD：可以增加(如果使用负数，就是减少)需要处理的任意长的时间。只要告诉它想要在那个日期上，以及想要在它上面添加的时间单位（天，星期，年，分钟等）。

通过WITH CHECK OPTION限制插入到视图中的内容

删除视图

审查：显示现有的代码

2.sys.sql_modules 元数据函数

语法：SELECT * FROM sys.sql_modules WHERE object_id = OBJECT_ID('dbo.YesterdaysOrders_vw');

定义：加密视图必须做的所有工作是使用WITH ENCRYPTION选项。

注意：1.WITH ENCRYPTION跟在视图的名称之后，单在AS关键字之前。

2.WITH ENCRYPTION不使用OPTION关键字。

案例：

ALTER VIEW CustomerOrders_vw
WITH ENCRYPTION
AS
SELECT 
sc.AccountNumber,
soh.SalesOrderID,
soh.OrderDate,
sod.ProductID,
pp.Name,
sod.OrderQty,
sod.UnitPrice,
sod.UnitPriceDiscount*sod.UnitPrice*sod.OrderQty AS TotalDiscount,
sod.LineTotal
 FROM 
Sales.Customer AS sc
INNER JOIN Sales.SalesOrderHeader AS soh
ON sc.CustomerID = soh.CustomerID
INNER JOIN Sales.SalesOrderDetail AS sod
ON soh.SalesOrderID = sod.SalesOrderID
INNER JOIN Production.Product AS pp
ON sod.ProductID = pp.ProductID;

案例：

ALTER VIEW CustomerOrders_vw
WITH SCHEMABINDING
AS
SELECT 
sc.AccountNumber,
soh.SalesOrderID,
soh.OrderDate,
sod.ProductID,
pp.Name,
sod.OrderQty,
sod.UnitPrice,
sod.UnitPriceDiscount*sod.UnitPrice*sod.OrderQty AS TotalDiscount,
sod.LineTotal
 FROM Sales.Customer AS sc
INNER JOIN Sales.SalesOrderHeader AS soh
ON sc.CustomerID = soh.CustomerID
INNER JOIN Sales.SalesOrderDetail AS sod
ON soh.SalesOrderID = sod.SalesOrderID
INNER JOIN Production.Product AS pp
ON sod.ProductID = pp.ProductID;

SELECT * FROM CustomerOrders_vw;

给视图创建群集索引

CREATE UNIQUE CLUSTERED INDEX ivCustomerOrders
ON CustomerOrders_vw(AccountNumber,SalesOrderID,ProductID);

案例：

CREATE VIEW CustomerTotalOrdersByDay_vw
WITH SCHEMABINDING
AS
SELECT 
SUM(sod.OrderQty) TotalOrderQty,
AVG(sod.UnitPrice) AveragePrice,
AVG(sod.UnitPriceDiscount*sod.UnitPrice*sod.OrderQty)
AS AverageDiscount,
SUM(sod.LineTotal) TotalSale
 FROM Sales.Customer AS sc
INNER JOIN Sales.SalesOrderHeader AS soh
ON sc.CustomerID = soh.CustomerID
INNER JOIN Sales.SalesOrderDetail AS sod
ON soh.SalesOrderID  = sod.SalesOrderID
GROUP BY soh.OrderDate;