C# in Depth

322 CHAPTER 12 LINQ beyond collectionsFROM [dbo].[DefectUser] AS [t0]) AS [t1]ORDER BY [t1].[value]This is a good example of where the generated SQL is wordier than it needs to be.Although we couldn’t reference the elements of the final output sequence when performingan ordering on the query expression, you can in SQL. This simpler querywould have worked fine:SELECT LEN([t0].[Name]) AS [value], [t0].[Name]FROM [dbo].[DefectUser] AS [t0]ORDER BY [value]Of course, what’s important is what the query optimizer does on the database—theexecution plan displayed in SQL Server Management Studio Express is the same forboth queries, so it doesn’t look like we’re losing out.Next we’ll have a look at a couple of the joins we used in chapter 11.EXPLICIT JOINS: MATCHING DEFECTS WITH NOTIFICATION SUBSCRIPTIONSWe’ll try both inner joins and group joins, using the examples of joining notificationsubscriptions against projects. I suspect you’re used to the drill now—the pattern ofthe code is the same for each query, so from here on I’ll just show the query expressionand the generated SQL unless something else is going on.// Query expression (modified from listing 11.12)from defect in context.Defectsjoin subscription in context.NotificationSubscriptionson defect.Project equals subscription.Projectselect new { defect.Summary, subscription.EmailAddress }-- Generated SQLSELECT [t0].[Summary], [t1].[EmailAddress]FROM [dbo].[Defect] AS [t0]INNER JOIN [dbo].[NotificationSubscription] AS [t1]ON [t0].[ProjectID] = [t1].[ProjectID]Unsurprisingly, it uses an inner join in SQL. It would be easy to guess at the generatedSQL in this case. How about a group join, though? Well, this is where things getslightly more hectic:// Query expression (modified from listing 11.13)from defect in context.Defectsjoin subscription in context.NotificationSubscriptionson defect.Project equals subscription.Projectinto groupedSubscriptionsselect new { Defect = defect, Subscriptions = groupedSubscriptions }-- Generated SQLSELECT [t0].[DefectID] AS [ID], [t0].[Created],[t0].[LastModified], [t0].[Summary], [t0].[Severity],[t0].[Status], [t0].[AssignedToUserID],[t0].[CreatedByUserID], [t0].[ProjectID],[t1].[NotificationSubscriptionID],[t1].[ProjectID] AS [ProjectID2], [t1].[EmailAddress],(SELECT COUNT(*)Licensed to Rhona Hadida