Question

我正在加入Entity Framwork中的两个对象，并将所有条件放在Where子句中。但我的老板说要将Where谓词中的所有其他条件放在更高效的位置。如下所示，第一个是我的版本 -

var query = from ct in dbContext.ClaimTrackings
                                            join cts in dbContext.ClaimTrackingStatus
                                            on ct.ID equals cts.ClaimTrackingID
                                            where ct.CenterID == centerID && ct.ClaimMonth == SharePointClaimProcessingData.ClaimMonth && ct.ClaimYear == SharePointClaimProcessingData.ClaimYear
                                            select cts;




var query = from ct in dbContext.ClaimTrackings.Where(p => p.CenterID == centerID && p.ClaimMonth == SharePointClaimProcessingData.ClaimMonth && p.ClaimYear == SharePointClaimProcessingData.ClaimYear)
                                            join cts in dbContext.ClaimTrackingStatus
                                            on ct.ID equals cts.ClaimTrackingID
                                            select cts;

我无法看到生成的脚本，因为此代码只能在生产中运行。我不确定哪一个更有效率。所以请解释一下。

Answer 1

好的，我已经做了一些测试，我认为是正确的 - 因为结果是一样的，将where子句移到更高的位置根本没有任何区别 - 当然对于SQL服务器。

只是在我们的一个客户端应用程序的上下文中运行了这两个查询（刚刚换出了我的实体名称）：

        var query = from ct in _context.Batches
                    join cts in _context.Blends
                    on ct.BatchId equals cts.BatchId
                    where ct.BatchId == 13349 && ct.CreatedBy == "Automation"
                    select cts;

        var query2 = from ct in _context.Batches.Where(x => x.BatchId == 13349 && x.CreatedBy == "Automation")
                     join cts in _context.Blends
                     on ct.BatchId equals cts.BatchId
                     select cts;

等效查询：

SELECT 
[Extent2].[BlendId] AS [BlendId], 
[Extent2].[BatchId] AS [BatchId], 
[Extent2].[BlendNumber] AS [BlendNumber], 
[Extent2].[ProductCode] AS [ProductCode], 
[Extent2].[TargetQuantity] AS [TargetQuantity], 
[Extent2].[RecipeDescription] AS [RecipeDescription], 
[Extent2].[BlenderId] AS [BlenderId], 
[Extent2].[TestingSetDescription] AS [TestingSetDescription], 
[Extent2].[SieveDefaultDescription] AS [SieveDefaultDescription], 
[Extent2].[ReblendTime] AS [ReblendTime], 
[Extent2].[Operator] AS [Operator], 
[Extent2].[ProcessedBy] AS [ProcessedBy], 
[Extent2].[KeggedBy] AS [KeggedBy], 
[Extent2].[ApprovedBy] AS [ApprovedBy], 
[Extent2].[ActualQuantity] AS [ActualQuantity], 
[Extent2].[TestedBy] AS [TestedBy], 
[Extent2].[TestStatus] AS [TestStatus], 
[Extent2].[ApprovedQuantity] AS [ApprovedQuantity], 
[Extent2].[CreatedDate] AS [CreatedDate]
FROM  [dbo].[Batches] AS [Extent1]
INNER JOIN [dbo].[Blends] AS [Extent2] ON [Extent1].[BatchId] = [Extent2].[BatchId]
WHERE (13349 = [Extent1].[BatchId]) AND (N'Automation' = [Extent1].[CreatedBy])

和

SELECT 
[Extent2].[BlendId] AS [BlendId], 
[Extent2].[BatchId] AS [BatchId], 
[Extent2].[BlendNumber] AS [BlendNumber], 
[Extent2].[ProductCode] AS [ProductCode], 
[Extent2].[TargetQuantity] AS [TargetQuantity], 
[Extent2].[RecipeDescription] AS [RecipeDescription], 
[Extent2].[BlenderId] AS [BlenderId], 
[Extent2].[TestingSetDescription] AS [TestingSetDescription], 
[Extent2].[SieveDefaultDescription] AS [SieveDefaultDescription], 
[Extent2].[ReblendTime] AS [ReblendTime], 
[Extent2].[Operator] AS [Operator], 
[Extent2].[ProcessedBy] AS [ProcessedBy], 
[Extent2].[KeggedBy] AS [KeggedBy], 
[Extent2].[ApprovedBy] AS [ApprovedBy], 
[Extent2].[ActualQuantity] AS [ActualQuantity], 
[Extent2].[TestedBy] AS [TestedBy], 
[Extent2].[TestStatus] AS [TestStatus], 
[Extent2].[ApprovedQuantity] AS [ApprovedQuantity], 
[Extent2].[CreatedDate] AS [CreatedDate]
FROM  [dbo].[Batches] AS [Extent1]
INNER JOIN [dbo].[Blends] AS [Extent2] ON [Extent1].[BatchId] = [Extent2].[BatchId]
WHERE (13349 = [Extent1].[BatchId]) AND (N'Automation' = [Extent1].[CreatedBy])

毫不奇怪他们是完全相同的。我无法为您提供EF用于生成查询的确切机制，但基本上您正在加入两个表并进行过滤，因此转换为商店查询会给您相同的结果，这很可能是因为它查看实体的方式参与

所以，在这种情况下，第二次猜测你的老板（我一直在做的事情）是正确的：）

在where子句中的where谓词之前的条件

1 个答案: