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POAdvanced multiple join in subquery using LINQ
 

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    <p>I have spent the afternoon trying to wrap my mind around how to translate the following query into LINQ, but I can't quite get there.</p> <pre><code>declare @productId int; set @productId = 3212; select * from InformationData data where productId = @productId and orgId = 1 and exists( select id from ( select coalesce(id1.id, id2.id, id3.id) as id from ( select productId,attributeId from InformationData where productId = @productId group by productId,attributeId ) id left outer join InformationData id1 on id1.productId = id.productId and id1.attributeId = id.attributeId and id1.language = 1 left outer join InformationData id2 on id2.productId = id.productId and id2.attributeId = id.attributeId and id2.language = 2 left outer join InformationData id3 on id3.productId = id.productId and id3.attributeId = id.attributeId and id3.language = 0 ) row where row.id = data.id ) </code></pre> <p>The purpose of the query is to fetch data from a table using 2 fallback languages, so if the data does not exist in language 1, it is fetched in language 2, and if 2 does not exists it is fetched for language 0 which is a global translation.</p> <p>I can get the inner query mostly correct (except from id1.language = 1, I can't seem to get it to join on a member of the table I'm joining to, any ideas?)</p> <p>This is my code (LINQPad code):</p> <pre><code>( from data in ( from d in InformationData where d.ProductId == 3212 group d by new { d.ProductId, d.AttributeId } into p select new { ProductId = p.Key.ProductId, AttributeId = p.Key.AttributeId } ) join x1 in InformationData on new { a = data.ProductId, b = data.AttributeId } equals new { a = x1.ProductId, b = x1.AttributeId } into f1 from r1 in f1.DefaultIfEmpty() where r1.Language == 1 join x2 in InformationData on new { a = data.ProductId, b = data.AttributeId } equals new { a = x2.ProductId, b = x2.AttributeId } into f2 from r2 in f2.DefaultIfEmpty() where r2.Language == 2 join x3 in InformationData on new { a = data.ProductId, b = data.AttributeId } equals new { a = x3.ProductId, b = x3.AttributeId } into f3 from r3 in f3.DefaultIfEmpty() where r3.Language == 2 select new { Id = ((int?)r1.Id) ?? ((int?)r2.Id) ?? r3.Id } ).Dump(); </code></pre> <p>Which generates the following SQL:</p> <pre><code>-- Region Parameters DECLARE @p0 Int SET @p0 = 3212 DECLARE @p1 Int SET @p1 = 2 DECLARE @p2 Int SET @p2 = 2 DECLARE @p3 Int SET @p3 = 1 -- EndRegion SELECT COALESCE([t2].[id],COALESCE([t3].[id],[t4].[id])) AS [Id] FROM ( SELECT [t0].[productId], [t0].[attributeId] FROM [InformationData] AS [t0] WHERE [t0].[productId] = @p0 GROUP BY [t0].[productId], [t0].[attributeId] ) AS [t1] LEFT OUTER JOIN [InformationData] AS [t2] ON ([t1].[productId] = [t2].[productId]) AND ([t1].[attributeId] = [t2].[attributeId]) LEFT OUTER JOIN [InformationData] AS [t3] ON ([t1].[productId] = [t3].[productId]) AND ([t1].[attributeId] = [t3].[attributeId]) LEFT OUTER JOIN [InformationData] AS [t4] ON ([t1].[productId] = [t4].[productId]) AND ([t1].[attributeId] = [t4].[attributeId]) WHERE ([t4].[language] = @p1) AND ([t3].[language] = @p2) AND ([t2].[language] = @p3) </code></pre> <p>But I can't put this together with the rest of the query, maybe I'm just tired buy I keep getting it to do a lot of CROSS APPLY's. Does anyone have any suggestions?</p>
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