视图使用SQL Server中的表值函数替代视图（sqlserver中代替）

Views Using Table-Valued Functions in SQL Server

The Microsoft SQL Server relational database management system provides a set of tools to store and manipulate data. A key feature in SQL Server is its ability to create stored procedures and views that represent sub-queries. Views are frequently used to limit access to only the data that is relevant to a particular user. Table-valued functions (TVF) are another type of SQL Server stored procedure that can also be used to return results as a virtual table. Using table-valued functions as an alternative to views can provide several benefits.

A table-valued function is like an ordinary stored procedure that returns an array of rows rather than a single value. This allows users to select data from the whole table, not just from one row. TVFs can accept input parameters to return specific subsets of data. This can be useful in creating dynamic views without having to create hardcoded SQL statements.

Using table-valued functions instead of views also offers performance benefits. In certain scenarios, such as large queries, TVFs can offer better performance than views due to more efficient caching and reuse. Because TVFs are compiled once and remain in memory, they can be quickly reused when called multiple times. Views, on the other hand, must be parsed and compiled the first time they are called and cannot be cached efficiently.

Not all operations that can be done with views can be done with TVFs. Joins, for example, must be performed in views, but not in TVFs. Additionally, TVFs cannot be used to emit triggers. Even so, using TVFs instead of views can provide many benefits, including the ability to accept input parameters and better performance in certain scenarios. Below is an example of a table-valued function in SQL Server:

“`sql

CREATE FUNCTION GetEmployeesByDepartment

@DepartmentID int

AS

BEGIN

SELECT *

FROM Employees

WHERE DepartmentID = @DepartmentID

END

GO

In this example, a table-valued function is created that accepts a single input parameter, @DepartmentID, that is used to return a set of employees from a particular department.
Table-valued functions can be used as an alternative to views in many cases in order to gain the benefits of better performance and the ability to accept input parameters. While not all operations that can be done with views can be done with TVFs, it is worth considering using TVFs instead of views for certain scenarios as they can offer unique advantages.