是否可以在视图中创建一个临时表并在选择后删除它?

问题描述

我需要改变一个视图，我想在 SELECT 之前引入 2 个临时表.

I need to alter one view and I want to introduce 2 temporary table before the SELECT.

这可能吗?我该怎么做?

Is this possible? And how can I do it?

ALTER VIEW myView
AS 

SELECT *
INTO #temporary1

SELECT *
INTO #temporary2

SELECT * FROM #temporary1
UNION ALL 
SELECT * FROM #temporary1

DROP TABLE #temporary1
DROP TABLE #temporary2

当我尝试这样做时，它抱怨 ALTER VIEW 必须是批处理中的唯一语句.

When I attempt this it complains that ALTER VIEW must be the only statement in the batch.

我怎样才能做到这一点?

How can I achieve this?

推荐答案

不，视图由单个 SELECT 语句组成.您不能在视图中创建或删除表.

No, a view consists of a single SELECT statement. You cannot create or drop tables in a view.

也许公用表表达式 (CTE) 可以解决您的问题.CTE 是在单个语句的执行范围内定义的临时结果集，它们可以在视图中使用.

Maybe a common table expression (CTE) can solve your problem. CTEs are temporary result sets that are defined within the execution scope of a single statement and they can be used in views.

示例(取自此处) - 您可以想到 SalesBySalesPerson CTE 作为临时表:

Example (taken from here) - you can think of the SalesBySalesPerson CTE as a temporary table:

CREATE VIEW vSalesStaffQuickStats
AS
  WITH SalesBySalesPerson (SalesPersonID, NumberOfOrders, MostRecentOrderDate)
      AS
      (
            SELECT SalesPersonID, COUNT(*), MAX(OrderDate)
            FROM Sales.SalesOrderHeader
            GROUP BY SalesPersonID
      )
  SELECT E.EmployeeID,
         EmployeeOrders = OS.NumberOfOrders,
         EmployeeLastOrderDate = OS.MostRecentOrderDate,
         E.ManagerID,
         ManagerOrders = OM.NumberOfOrders,
         ManagerLastOrderDate = OM.MostRecentOrderDate
  FROM HumanResources.Employee AS E
  INNER JOIN SalesBySalesPerson AS OS ON E.EmployeeID = OS.SalesPersonID
  LEFT JOIN SalesBySalesPerson AS OM ON E.ManagerID = OM.SalesPersonID
GO

性能注意事项

哪个性能更好，CTE 表还是临时表?

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