Question

我有以下观点：

SELECT     
poHeader.No_ AS PONumber, 
poHeader.[Buy-from Vendor No_] AS VendorNumber, 
poHeader.[Document Date] AS DocumentDate, 
vendor.Name AS VendorName, 
vendor.Contact AS VendorContact, 
vendor.[E-Mail] AS VendorEmail, 
vendor.Address AS VendorAddress, 
vendor.[Address 2] AS VendorAddress2, 
vendor.City AS VendorCity, 
vendor.County AS VendorCounty, 
vendor.[Post Code] AS VendorPostCode, 
vendor.[Phone No_] AS VendorPhone, 
vendor.[Fax No_] AS VendorFax, 
salesHeader.No_ AS SONumber, 
poHeader.[Order Date] AS OrderDate, 
salesHeader.[Crocus Comment] AS CrocusComment, 
salesHeader.GiftMessage, 
salesHeader.[Delivery Comment] AS DeliveryComment, 
salesHeader.[Shipment Date] AS DeliveryDate, 
COALESCE (salesHeader.[Ship-to Name], 
poHeader.[Ship-to Name]) AS DeliveryName, 
COALESCE (salesHeader.[Ship-to Address],
poHeader.[Ship-to Address]) AS DeliveryAddress, 
COALESCE (salesHeader.[Ship-to Address 2],
poHeader.[Ship-to Address 2]) AS DeliveryAddress2,
COALESCE (salesHeader.[Ship-to City], 
poHeader.[Ship-to City]) AS DeliveryCity, COALESCE (salesHeader.[Ship-to County], 
poHeader.[Ship-to County]) AS DeliveryCounty, 
COALESCE (salesHeader.[Ship-to Post Code], 
poHeader.[Ship-to Post Code]) AS DeliveryPostcode, 
salesHeader.DeliveryPhoneNo, poForEmailing.Processed, 
poForEmailing.Copied

FROM         
Navision4.dbo.[Crocus Live$Purch_ orders for e-mailing] AS poForEmailing 
LEFT OUTER JOIN
Navision4.dbo.[Crocus Live$Purchase Header] AS poHeader ON poForEmailing.No_ = poHeader.No_ 
INNER JOIN
Navision4.dbo.[Crocus Live$Vendor] AS vendor ON poHeader.[Buy-from Vendor No_] = vendor.No_ 
LEFT OUTER JOIN
Navision4.dbo.[Crocus Live$Sales Header] AS salesHeader ON salesHeader.No_ = dbo.fnGetSalesOrderNumber(poHeader.No_)

此视图在名为NavisionMeta的数据库中创建它查询一个数据库（在同一台服务器上）claled Navision4

我最近将两个数据库都移到了新的（更好的）硬件上。不确定这是否相关，但新硬件有SQL 2008，旧硬件运行SQL 2000

如果我在SQL Management Studio中使用此查询查询它，则需要2分钟以上：

SELECT * 
FROM [NavisionMeta].[dbo].[PurchaseOrders]
WHERE Processed=0 AND Copied=0

太长时间了！

即使我将超时调整为5分钟，LINQ中的以下查询也会一起超时！

            var purchaseOrdersNotProcessed = (from p in db.PurchaseOrders
                                              where p.Copied.Equals(0)
                                              && p.Processed.Equals(0)
                                              select p).ToList();

让我感到困惑的是，在之前的硬件上，它运行良好！

以防它是相关的，上面使用的udf是：

CREATE FUNCTION [dbo].[fnGetSalesOrderNumber](@PONumber varchar(20))
RETURNS varchar(20)
AS
BEGIN

RETURN (
SELECT 
    TOP 1 [Sales Order No_]
FROM 
    Navision4.dbo.[Crocus Live$Purchase Line]
WHERE 
    [Document No_] = @PONumber
)

Answer 1

您也可以考虑更新统计信息。

Answer 2

左内加入？嗯，不确定这是否会有所帮助......

如果此查询之前有效（数据不是性能），则上述查询将从将所有连接转换为INNER JOIN中受益。因为你是来自poHeader（外连接）的值的INNER JOINing供应商，所以你基本上也在poHeader上建立了一个内连接要求（除了外连接的潜在性能命中）。除非poHeader具有值，并且供应商是内连接的，否则供应商不能返回值，如果poHeader中没有值，则将忽略整行。与salesHeader相同。连接中使用的函数需要poHeader中的值（必须具有根据上述逻辑的值），因此此连接也可以从显式的INNER JOIN中获益，而不仅仅是隐含的连接。

除此之外，我同意关于索引的陈述（除了关于外连接的陈述很少。这就像说如果你有锤子你不需要螺丝刀）。索引听起来像是对性能较弱的最合乎逻辑的解释。具体来说，您应该检查poForEmailing别名表是否有索引（[processed]，[copied]）。如果没有该索引，您可以期望查询时间至少加倍，因为数据大小加倍，因为该表中的每个记录都需要针对这些谓词进行测试。关于你原来的问题，我没有注意到SQL Server 2008中任何表明性能发生这种变化的东西，其他条件都相同。

Answer 3

一个起点可能是在旧机器和新机器上查看查询的执行计划。对于较新版本的SQL Server，肯定存在优化差异。执行计划可能会向您显示索引是必要的，由于某种原因，索引在先前版本中并不那么重要。

Answer 4

修改

我不确定你要做什么，但如果你想获得有关PO的信息，我认为下面的更改会有所帮助，你有

FROM Navision4.dbo.[Crocus Live$Purch_ orders for e-mailing] AS poForEmailing LEFT OUTER JOIN Navision4.dbo.[Crocus Live$Purchase Header] AS poHeader ON poForEmailing.No_ = poHeader.No_ INNER JOIN Navision4.dbo.[Crocus Live$Vendor] AS vendor ON poHeader.[Buy-from Vendor No_] = vendor.No_ LEFT OUTER JOIN Navision4.dbo.[Crocus Live$Sales Header] AS salesHeader ON salesHeader.No_ = dbo.fnGetSalesOrderNumber(poHeader.No_)

试试这个：

FROM Navision4.dbo.[Crocus Live$Purch_ orders for e-mailing] AS poForEmailing LEFT JOIN Navision4.dbo.[Crocus Live$Purchase Header] AS poHeader ON poForEmailing.No_ = poHeader.No_ LEFT JOIN Navision4.dbo.[Crocus Live$Vendor] AS vendor ON poHeader.[Buy-from Vendor No_] = vendor.No_ LEFT JOIN Navision4.dbo.[Crocus Live$Sales Header] AS salesHeader ON salesHeader.No_ = dbo.fnGetSalesOrderNumber(poHeader.No_)

就速度而言，您可能需要更新一些索引...尤其是No_字段。另外进行以下更改以消除每行调用的fuGetSalesOrderNumber（）：

;WITH PurchaseLineByPO AS ( SELECT MAX([Sales Order No_]) as SO, [Document No_] as DNum FROM Navision4.dbo.[Crocus Live$Purchase Line] Group By [Document No_] ) --blah blah whole select goes here.. with JOIN PurchaseLineByPO ON DNum = poHeader.No_ --in the join and LEFT OUTER JOIN Navision4.dbo.[Crocus Live$Sales Header] AS salesHeader ON salesHeader.No_ = PurchaseLineByPO.SO --replaces what you had

看看它是否适合你。

忽略下面的旧内容......

我很难确切地看到你在这里做了什么，但是很少需要OUTER连接 - 这实际上是你想做什么的？如果是，您可以撤消订单并进行内部联接。例如，你说：

FROM Navision4.dbo.[Crocus Live$Purch_ orders for e-mailing] AS poForEmailing LEFT OUTER JOIN Navision4.dbo.[Crocus Live$Purchase Header] AS poHeader ON poForEmailing.No_ = poHeader.No_

你可以说

FROM Navision4.dbo.[Crocus Live$Purchase Header] AS poHeader LEFT INNER JOIN Navision4.dbo.[Crocus Live$Purch_ orders for e-mailing] AS poForEmailing ON poForEmailing.No_ = poHeader.No_

根据您的数据，这可能会对您的运行时间产生重大影响。

查询视图时响应缓慢 - 使用Linq to SQL

4 个答案: