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SQL OVER（）句-いつ、なぜ役立つのですか？
USE AdventureWorks2008R2; GO SELECT SalesOrderID, ProductID, OrderQty ,SUM(OrderQty) OVER(PARTITION BY SalesOrderID) AS 'Total' ,AVG(OrderQty) OVER(PARTITION BY SalesOrderID) AS 'Avg' ,COUNT(OrderQty) OVER(PARTITION BY SalesOrderID) AS 'Count' ,MIN(OrderQty) OVER(PARTITION BY SalesOrderID) AS 'Min' ,MAX(OrderQty) OVER(PARTITION BY SalesOrderID) AS 'Max' FROM Sales.SalesOrderDetail WHERE SalesOrderID IN(43659,43664); その条項について読みましたが、なぜ必要なのかわかりません。関数Overは何をしますか？何をしPartitioning Byますか？なぜ書き込みでクエリを実行できないのGroup By SalesOrderIDですか？