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• How can I join this 2 queries?(A select query with join and An unpivot query)

  - by MANG KANOR

  Here are my two queries SELECT EWND.Position, NKey = CASE WHEN ISNULL(Translation.Name, '') = '' THEN EWND.Name ELSE Translation.Name END, Unit = EW_N_DEF.Units FROM EWND INNER JOIN EW_N_DEF ON EW_N_DEF.Nutr_No = EWND.Nutr_No LEFT JOIN Translation ON Translation.CodeMain = EWND.Nutr_no WHERE Translation.CodeTrans = 1 ORDER BY EWND.Position And this is the unpivot one SELECT * FROM (SELECT N1,N2,N3,N4,N5,N6,N7,N8,N9,N10,N11,N12,N13,N14,N15,N16,N17,N18,N19,N20,N21,N22,N23,N24,N25,N26,N27,N28,N29,N30,N31,N32,N33,N34 FROM EWNVal WHERE Code=6035) Test UNPIVOT (Value FOR NUTCODE IN (N1,N2,N3,N4,N5,N6,N7,N8,N9,N10,N11,N12,N13,N14,N15,N16,N17,N18,N19,N20,N21,N22,N23,N24,N25,N26,N27,N28,N29,N30,N31,N32,N33,N34) )AS test Both Queries put out same number of rows but not columns, Is it possible to join this two? I tried the union but it has problems that I cant solve Thanks in advance!

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• Get recursive data with sql server

  - by user228777

  I am trying to get recursive data. Following code returns all parents on the top and then the children. I would like to get data Parent 1 – his children then parent 2 - his children then parent3 – his children. How do I do this? USE Subscriber GO WITH Parent (ParentId, Id, Name,subscriberID) AS ( -- Anchor member definition SELECT A.ParentId,A.id, A.name,A.SubscriberId FROM Subscriber.Budget.SubscriberCategory AS A WHERE ParentId IS NULL UNION ALL -- Recursive member definition SELECT B.ParentId, B.id, B.name,B.SubscriberId FROM Subscriber.Budget.SubscriberCategory AS B INNER JOIN Parent AS P ON B.ParentId = P.Id ) -- Statement that executes the CTE SELECT parentId, id, name FROM Parent where subscriberID = '1C18093B-5031-42E4-9251-CEF69114365F' GO

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• Linq to SQL and concurrency with Rob Conery repository pattern

  - by David Hall

  I have implemented a DAL using Rob Conery's spin on the repository pattern (from the MVC Storefront project) where I map database objects to domain objects using Linq and use Linq to SQL to actually get the data. This is all working wonderfully giving me the full control over the shape of my domain objects that I want, but I have hit a problem with concurrency that I thought I'd ask about here. I have concurrency working but the solution feels like it might be wrong (just one of those gitchy feelings). The basic pattern is: private MyDataContext _datacontext private Table _tasks; public Repository(MyDataContext datacontext) { _dataContext = datacontext; } public void GetTasks() { _tasks = from t in _dataContext.Tasks; return from t in _tasks select new Domain.Task { Name = t.Name, Id = t.TaskId, Description = t.Description }; } public void SaveTask(Domain.Task task) { Task dbTask = null; // Logic for new tasks omitted... dbTask = (from t in _tasks where t.TaskId == task.Id select t).SingleOrDefault(); dbTask.Description = task.Description, dbTask.Name = task.Name, _dataContext.SubmitChanges(); } So with that implementation I've lost concurrency tracking because of the mapping to the domain task. I get it back by storing the private Table which is my datacontext list of tasks at the time of getting the original task. I then update the tasks from this stored Table and save what I've updated This is working - I get change conflict exceptions raised when there are concurrency violations, just as I want. However, it just screams to me that I've missed a trick. Is there a better way of doing this? I've looked at the .Attach method on the datacontext but that appears to require storing the original version in a similar way to what I'm already doing. I also know that I could avoid all this by doing away with the domain objects and letting the Linq to SQL generated objects all the way up my stack - but I dislike that just as much as I dislike the way I'm handling concurrency.

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• Delphi Prism and LINQ to SQL / Entity Framework

  - by Vegar

  I have found many posts and examples of using LINQ-syntax in Delphi Prism (Oxygene), but I have never found anything on LINQ to SQL or Entity Framework. Is it possible to use LINQ to SQL or Entity Framework together with Prism? Where can I found such an example? Update: Olaf is giving an answer through his blog The question is now if any visual tools and code generation is provided, or if everything must be done by hand... Second update: Olaf has answered the tool/code generation-question in a comment on his site: The class designer is there, but there is no Pascal code gen. According to marc hoffman that is currently not on their list. For now you have to live with manual mapping. I guess, if you had Visual Studio (not just the VS shell), that you could add a C# library project to your solution, reference that from your Prism project. Then create the Table-Class mapping in the C# project using the visual designer. Maybe somewhat ugly, but possibly the key to get the Designer + CodeGen integrated into Prism. Who cares what language is used for the mapping . I will say this is a 1 - 0 to c# vs prism. If I did not care which language is used for the mapping - why should I care about which language is used for the rest?

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• LINQ into SortedList

  - by Chris Simmons

  I'm a complete LINQ newbie, so I don't know if my LINQ is incorrect for what I need to do or if my expectations of performance are too high. I've got a SortedList of objects, keyed by int; SortedList as opposed to SortedDictionary because I'll be populating the collection with pre-sorted data. My task is to find either the exact key or, if there is no exact key, the one with the next higher value. If the search is too high for the list (e.g. highest key is 100, but search for 105), return null. // The structure of this class is unimportant. Just using // it as an illustration. public class CX { public int KEY; public DateTime DT; } static CX getItem(int i, SortedList<int, CX> list) { var items = (from kv in list where kv.Key >= i select kv.Key); if (items.Any()) { return list[items.Min()]; } return null; } Given a list of 50,000 records, calling getItem 500 times takes about a second and a half. Calling it 50,000 times takes over 2 minutes. This performance seems very poor. Is my LINQ bad? Am I expecting too much? Should I be rolling my own binary search function?

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• LINQ-to-SQL: Could not find key member 'x' of key 'x' on type 'y'

  - by Austin Hyde

  I am trying to connect my application to a SQLite database with LINQ-to-SQL, and so far everything has worked fine. The only hitch was that the SQLite provider I am using does not support code generation (unless I was doing something wrong), so I manually coded the 4 tables in the DB. The solution builds properly, but will not run, giving me the error message Could not find key member 'ItemType_Id' of key 'ItemType_Id' on type 'Item'. The key may be wrong or the field or property on 'Item' has changed names. I have checked and double checked spellings and field names on the database and in the attribute mappings, but could not find any problems. The SQL for the table looks like this: CREATE TABLE [Items] ( [Id] integer PRIMARY KEY AUTOINCREMENT NOT NULL, [Name] text NOT NULL, [ItemType_Id] integer NOT NULL ); And my mapping code: [Table(Name="Items")] class Item { // [snip] [Column(Name = "Id", IsPrimaryKey=true, IsDbGenerated=true)] public int Id { get; set; } // [snip] [Column(Name="ItemType_Id")] public int ItemTypeId { get; set; } [Association(Storage = "_itemType", ThisKey = "ItemType_Id")] public ItemType ItemType { get { return _itemType.Entity; } set { _itemType.Entity = value; } } private EntityRef<ItemType> _itemType; // [snip] } This is really my first excursion into LINQ-to-SQL, and am learning as I go, but I cannot seem to get past this seeming simple problem. Why cannot LINQ see my association?

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• extracting RDL data using LINQ

  - by BobC

  I'm working with some SQL Report definition files (RDLs), using LINQ to extract component query statements for validation. I'm trying to extract the <DataSet> elements from under the <DataSets> element. I seem to be getting hung up with one of the elements under <DataSet><Fields><Field> which has a namespace qualifier <rd:TypeName> I've been using LINQ to XML for other parts of the files where there is no namespace qualifiers with no trouble, by specifying a default namespace. The RDL specifies two namespaces: xmlns="http://schemas.microsoft.com/sqlserver/reporting/2005/01/reportdefinition" xmlns:rd="http://schemas.microsoft.com/SQLServer/reporting/reportdesigner"> When I try to get the <DataSets> element, however, I get the following error: System.Xml.XmlException - The ':' character, hexadecimal value 0x3A, cannot be included in a name. I know it has to do with the namespace qualifier (rd:) in one of the child elements, but I'm having difficulty getting a LINQ expression that works. Any help would be appreciated. Thanks!

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• Linq: the linked objects are null, why?

  - by user46503

  Hello, I have several linked tables (entities). I'm trying to get the entities using the following linq: ObjectQuery<Location> locations = context.Location; ObjectQuery<ProductPrice> productPrice = context.ProductPrice; ObjectQuery<Product> products = context.Product; IQueryable<ProductPrice> res1 = from pp in productPrice join loc in locations on pp.Location equals loc join prod in products on pp.Product equals prod where prod.Title.ToLower().IndexOf(Word.ToLower()) > -1 select pp; This query returns 2 records, ProductPrice objects that have linked object Location and Product but they are null and I cannot understand why. If I try to fill them in the linq as below: res = from pp in productPrice join loc in locations on pp.Location equals loc join prod in products on pp.Product equals prod where prod.Title.ToLower().IndexOf(Word.ToLower()) > -1 select new ProductPrice { ProductPriceId = pp.ProductPriceId, Product = prod }; I have the exception "The entity or complex type 'PBExplorerData.ProductPrice' cannot be constructed in a LINQ to Entities query" Could someone please explain me what happens and what I need to do? Thanks

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• C# LINQ to XML nissing space character.

  - by Fossaw

  I write an XML file "by hand", (i.e. not with LINQ to XML), which sometimes includes an open/close tag containing a single space character. Upon viewing the resulting file, all appears correct, example below... <Item> <ItemNumber>3</ItemNumber> <English> </English> <Translation>Ignore this one. Do not remove.</Translation> </Item> ... the reasons for doing this are various and irrelevent, it is done. Later, I use a C# program with LINQ to XML to read the file back and extract the record... XElement X_EnglishE = null; // This is CRAZY foreach (XElement i in Records) { X_EnglishE = i.Element("English"); // There is only one damned record! } string X_English = X_EnglishE.ToString(); ... and test to make sure it is unchanged from the database record. I detect a change, when processing Items where the field had the single space character... +E+ Text[3] English source has been altered: Was: >>> <<< Now: >>><<< ... the and <<< parts I added to see what was happening, (hard to see space characters). I have fiddled around with this but can't see why this is so. It is not absolutely critical, as the field is not used, (yet), but I cannot trust C# or LINQ or whatever is doing this, if I do not understand why it is so. So what is doing that and why?

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• Is SQL Server DRI (ON DELETE CASCADE) slow?

  - by Aaronaught

  I've been analyzing a recurring "bug report" (perf issue) in one of our systems related to a particularly slow delete operation. Long story short: It seems that the CASCADE DELETE keys were largely responsible, and I'd like to know (a) if this makes sense, and (b) why it's the case. We have a schema of, let's say, widgets, those being at the root of a large graph of related tables and related-to-related tables and so on. To be perfectly clear, deleting from this table is actively discouraged; it is the "nuclear option" and users are under no illusions to the contrary. Nevertheless, it sometimes just has to be done. The schema looks something like this: Widgets | +--- Anvils (1:1) | | | +--- AnvilTestData (1:N) | +--- WidgetHistory (1:N) | +--- WidgetHistoryDetails (1:N) Nothing too scary, really. A Widget can be different types, an Anvil is a special type, so that relationship is 1:1 (or more accurately 1:0..1). Then there's a large amount of data - perhaps thousands of rows of AnvilTestData per Anvil collected over time, dealing with hardness, corrosion, exact weight, hammer compatibility, usability issues, and impact tests with cartoon heads. Then every Widget has a long, boring history of various types of transactions - production, inventory moves, sales, defect investigations, RMAs, repairs, customer complaints, etc. There might be 10-20k details for a single widget, or none at all, depending on its age. So, unsurprisingly, there's a CASCADE DELETE relationship at every level here. If a Widget needs to be deleted, it means something's gone terribly wrong and we need to erase any records of that widget ever existing, including its history, test data, etc. Again, nuclear option. Relations are all indexed, statistics are up to date. Normal queries are fast. The system tends to hum along pretty smoothly for everything except deletes. Getting to the point here, finally, for various reasons we only allow deleting one widget at a time, so a delete statement would look like this: DELETE FROM Widgets WHERE WidgetID = @WidgetID Pretty simple, innocuous looking delete... that takes over 2 minutes to run, for a widget with no data! After slogging through execution plans I was finally able to pick out the AnvilTestData and WidgetHistoryDetails deletes as the sub-operations with the highest cost. So I experimented with turning off the CASCADE (but keeping the actual FK, just setting it to NO ACTION) and rewriting the script as something very much like the following: DECLARE @AnvilID int SELECT @AnvilID = AnvilID FROM Anvils WHERE WidgetID = @WidgetID DELETE FROM AnvilTestData WHERE AnvilID = @AnvilID DELETE FROM WidgetHistory WHERE HistoryID IN ( SELECT HistoryID FROM WidgetHistory WHERE WidgetID = @WidgetID) DELETE FROM Widgets WHERE WidgetID = @WidgetID Both of these "optimizations" resulted in significant speedups, each one shaving nearly a full minute off the execution time, so that the original 2-minute deletion now takes about 5-10 seconds - at least for new widgets, without much history or test data. Just to be absolutely clear, there is still a CASCADE from WidgetHistory to WidgetHistoryDetails, where the fanout is highest, I only removed the one originating from Widgets. Further "flattening" of the cascade relationships resulted in progressively less dramatic but still noticeable speedups, to the point where deleting a new widget was almost instantaneous once all of the cascade deletes to larger tables were removed and replaced with explicit deletes. I'm using DBCC DROPCLEANBUFFERS and DBCC FREEPROCCACHE before each test. I've disabled all triggers that might be causing further slowdowns (although those would show up in the execution plan anyway). And I'm testing against older widgets, too, and noticing a significant speedup there as well; deletes that used to take 5 minutes now take 20-40 seconds. Now I'm an ardent supporter of the "SELECT ain't broken" philosophy, but there just doesn't seem to be any logical explanation for this behaviour other than crushing, mind-boggling inefficiency of the CASCADE DELETE relationships. So, my questions are: Is this a known issue with DRI in SQL Server? (I couldn't seem to find any references to this sort of thing on Google or here in SO; I suspect the answer is no.) If not, is there another explanation for the behaviour I'm seeing? If it is a known issue, why is it an issue, and are there better workarounds I could be using?

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• C# LINQ to XML missing space character.

  - by Fossaw

  I write an XML file "by hand", (i.e. not with LINQ to XML), which sometimes includes an open/close tag containing a single space character. Upon viewing the resulting file, all appears correct, example below... <Item> <ItemNumber>3</ItemNumber> <English> </English> <Translation>Ignore this one. Do not remove.</Translation> </Item> ... the reasons for doing this are various and irrelevent, it is done. Later, I use a C# program with LINQ to XML to read the file back and extract the record... XElement X_EnglishE = null; // This is CRAZY foreach (XElement i in Records) { X_EnglishE = i.Element("English"); // There is only one damned record! } string X_English = X_EnglishE.ToString(); ... and test to make sure it is unchanged from the database record. I detect a change, when processing Items where the field had the single space character... +E+ Text[3] English source has been altered: Was: >>> <<< Now: >>><<< ... the and <<< parts I added to see what was happening, (hard to see space characters). I have fiddled around with this but can't see why this is so. It is not absolutely critical, as the field is not used, (yet), but I cannot trust C# or LINQ or whatever is doing this, if I do not understand why it is so. So what is doing that and why?

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• Trouble with LINQ databind to GridView and RowDataBound

  - by Michael

  Greetings all, I am working on redesigning my personal Web site using VS 2008 and have chosen to use LINQ to create by data-access layer. Part of my site will be a little app to help manage my budget better. My first LINQ query does successfully execute and display in a GridView, but when I try to use a RowDataBound event to work with the results and refine them a bit, I get the error: The type or namespace name 'var' could not be found (are you missing a using directive or an assembly reference?) This interesting part is, if I just try to put in a var s = "s"; anywhere else in the same file, I get the same error too. If I go to other files in the web project, var s = "s"; compiles fine. Here is the LINQ Query call: public static IQueryable pubGetRecentTransactions(int param_accountid) { clsDataContext db; db = new clsDataContext(); var query = from d in db.tblMoneyTransactions join p in db.tblMoneyTransactions on d.iParentTransID equals p.iTransID into dp from p in dp.DefaultIfEmpty() where d.iAccountID == param_accountid orderby d.dtTransDate descending, d.iTransID ascending select new { d.iTransID, d.dtTransDate, sTransDesc = p != null ? p.sTransDesc : d.sTransDesc, d.sTransMemo, d.mTransAmt, d.iCheckNum, d.iParentTransID, d.iReconciled, d.bIsTransfer }; return query; } protected void Page_Load(object sender, EventArgs e) { if (!this.IsPostBack) { this.prvLoadData(); } } internal void prvLoadData() { prvCtlGridTransactions.DataSource = clsMoneyTransactions.pubGetRecentTransactions(2); prvCtlGridTransactions.DataBind(); } protected void prvCtlGridTransactions_RowDataBound(object sender, GridViewRowEventArgs e) { if (e.Row.RowType == DataControlRowType.DataRow) { var datarow = e.Row.DataItem; var s = "s"; e.Row.Cells[0].Text = datarow.dtTransDate.ToShortDateString(); e.Row.Cells[1].Text = datarow.sTransDesc; e.Row.Cells[2].Text = datarow.mTransAmt.ToString("c"); e.Row.Cells[3].Text = datarow.iReconciled.ToString(); }//end if }//end RowDataBound My googling to date hasn't found a good answer, so I turn it over to this trusted community. I appreciate your time in assisting me.

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• oData/ADO.NET Data Services using LINQ-to-SQL with a decryption layer

  - by Program.X

  I have written an application using LINQ-to-SQL that submits a web form into a database. I absact the LINQ-to-SQL away using a Repository pattern. This repository has the basic methods: Get(), Save(), etc. As a development of the project, I needed to encrypt certain fields in the form. This was trivial, as I just added the encryption calls to the Get(), Save() methods in the Repository. Now, I want to put an oData layer over it, to allow RESTful extraction from MS Excel 2010 (when it comes out). I have this working, after a few stumbles on useless error messages, etc. However, obviously, those encrypted fields are still encrypted. My repository pattern would have decrypted these for me. As far as I know, I have to directly bind my oData service to the LINQ-to-SQL context for the schema, etc. to work - unless I enter a whole world of pain (any URLs appreciated). Is there a way I can insert my encryption/decryption layer into the request so decryption is done "on the fly"? I looked at the OnStartProcessingRequest() overload of DataService but this doesn't seem that useful.

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• Update mapping table in Linq

  - by Gary McGill

  I have a table Customers with a CustomerId field, and a table of Publications with a PublicationId field. Finally, I have a mapping table CustomersPublications that records which publications a customer can access - it has two fields: CustomerId field PublicationId. For a given customer, I want to update the CustomersPublications table based on a list of publication ids. I want to remove records in CustomersPublications where the PublicationId is not in the list, and add new records where the PublicationId is in the list but not already in the table. This would be easy in SQL, but I can't figure out how to do it in Linq. For the delete part, I tried: var recordsToDelete = dataContext.CustomersPublications.Where ( cp => (cp.CustomerId == customerId) && ! publicationIds.Contains(cp.PublicationId) ); dataContext.CustomersPublications.DeleteAllOnSubmit(recordsToDelete); ... but that didn't work. I got an error: System.NotSupportedException: Method 'Boolean Contains(Int32)' has no supported translation to SQL So, I tried using Any(), as follows: var recordsToDelete = dataContext.CustomersPublications.Where ( cp => (cp.CustomerId == customerId) && ! publicationIds.Any(p => p == cp.PublicationId) ); ... and this just gives me another error: System.NotSupportedException: Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator Any pointers? [I have to say, I find Linq baffling (and frustrating) for all but the simplest queries. Better error messages would help!]

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• LINQ to XML contents of child records.

  - by Fossaw

  I have this LINQ to XML enquiry... var Records = from Item in XDoc.Root.Elements("Item") where (string)Item.Element("ItemNumber") == item.ID.ToString select Item; ... where ItemNumber is a reference number used in the XML, (originally written by this program but manually edited by "others"), and item.ID is the database version of the same thing. The query executes, and I can test for the number of entries in the result fine... if (Records.Count() < 1) ... you get the idea. I have established that there is only one record. Each Item has several child fields. I want to test the values of the child fields are reasonable before passing them on to the database update sub-system. The XML is produced by the program, but edited by users, so I need to really check what is coming back. So I tried... if (DB_English.ToString() != Records.Elements("English").ToString()) ... DB_English is from the database, but the XML in Records, does not contain the contents of that field, it contains... System.Xml.Linq.Extensions+<GetElements>d__29`1[System.Xml.Linq.XElement] ... so, how do I get the value of this element in the XML file? I need to check the field in the XML has not been altered, (the manual editors of this data file are not potentially 100% reliable).

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• Need advice on comparing the performance of 2 equivalent linq to sql queries

  - by uvita

  I am working on tool to optimize linq to sql queries. Basically it intercepts the linq execution pipeline and makes some optimizations like for example removing a redundant join from a query. Of course, there is an overhead in the execution time before the query gets executed in the dbms, but then, the query should be processed faster. I don't want to use a sql profiler because I know that the generated query will be perform better in the dbms than the original one, I am looking for a correct way of measuring the global time between the creation of the query in linq and the end of its execution. Currently, I am using the Stopwatch class and my code looks something like this: var sw = new Stopwatch(); sw.Start(); const int amount = 100; for (var i = 0; i < amount; i++) { ExecuteNonOptimizedQuery(); } sw.Stop(); Console.Writeline("Executing the query {2} times took: {0}ms. On average, each query took: {1}ms", sw.ElapsedMilliseconds, sw.ElapsedMilliseconds / amount, amount); Basically the ExecutenNonOptimizedQuery() method creates a new DataContext, creates a query and then iterates over the results. I did this for both versions of the query, the normal one and the optimized one. I took the idea from this post from Frans Bouma. Is there any other approach/considerations I should take? Thanks in advance!

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• Get mutually and non mutually existening Fields in same table in Two columns

  - by ranabra

  This is a question similar to another question I posted here but is a little different. I am trying to get a list of all instances of mutual and non-mutual existing Users. What I mean is that the returned result from the query will return a list of users along with their co-worker. It is similar to the question here, but the difference is that non mutual users will be returned too and with out the "duplicity" mutually existing users return in the list (See image below in-order simplify it all). I took the original answer from Thomas (Thanx again Thomas) Select D1.u_username, U1.Permission, U1.Grade, D1.f_username, U2.Permission, U2.Gradefrom tblDynamicUserList As D1    Join tblDynamicUserList As D2        On D2.u_username = D1.f_username            And D2.f_username = D1.u_username    Join tblUsers As U1        On U1.u_username = D1.u_username    Join tblUsers As U2        On U2.u_username = D2.u_username and after some several trials I commented out 2 lines (Below). The returned result are exactly as described in the beginning of this question, but with the "duplicity" returned by mutually existing users in the table. How can I eliminate this duplicity? Select D1.u_username, U1.Permission, U1.Grade, D1.f_username, U2.Permission, U2.Gradefrom tblDynamicUserList As D1    Join tblDynamicUserList As D2        On D2.u_username = D1.f_username            /* And D2.f_username = D1.u_username */    Join tblUsers As U1        On U1.u_username = D1.u_username    Join tblUsers As U2        On U2.u_username = D2.u_username /* WHERE D1.U_userName < D1.f_username */ *Screenshot that hopefully helps explain it all. Database is SQL 2005. Many thanx in advance

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• Is there a way to delay compilation of a stored procedure's execution plan?

  - by Ian Henry

  (At first glance this may look like a duplicate of http://stackoverflow.com/questions/421275 or http://stackoverflow.com/questions/414336, but my actual question is a bit different) Alright, this one's had me stumped for a few hours. My example here is ridiculously abstracted, so I doubt it will be possible to recreate locally, but it provides context for my question (Also, I'm running SQL Server 2005). I have a stored procedure with basically two steps, constructing a temp table, populating it with very few rows, and then querying a very large table joining against that temp table. It has multiple parameters, but the most relevant is a datetime "@MinDate." Essentially: create table #smallTable (ID int) insert into #smallTable select (a very small number of rows from some other table) select * from aGiantTable inner join #smallTable on #smallTable.ID = aGiantTable.ID inner join anotherTable on anotherTable.GiantID = aGiantTable.ID where aGiantTable.SomeDateField > @MinDate If I just execute this as a normal query, by declaring @MinDate as a local variable and running that, it produces an optimal execution plan that executes very quickly (first joins on #smallTable and then only considers a very small subset of rows from aGiantTable while doing other operations). It seems to realize that #smallTable is tiny, so it would be efficient to start with it. This is good. However, if I make that a stored procedure with @MinDate as a parameter, it produces a completely inefficient execution plan. (I am recompiling it each time, so it's not a bad cached plan...at least, I sure hope it's not) But here's where it gets weird. If I change the proc to the following: declare @LocalMinDate datetime set @LocalMinDate = @MinDate --where @MinDate is still a parameter create table #smallTable (ID int) insert into #smallTable select (a very small number of rows from some other table) select * from aGiantTable inner join #smallTable on #smallTable.ID = aGiantTable.ID inner join anotherTable on anotherTable.GiantID = aGiantTable.ID where aGiantTable.SomeDateField > @LocalMinDate Then it gives me the efficient plan! So my theory is this: when executing as a plain query (not as a stored procedure), it waits to construct the execution plan for the expensive query until the last minute, so the query optimizer knows that #smallTable is small and uses that information to give the efficient plan. But when executing as a stored procedure, it creates the entire execution plan at once, thus it can't use this bit of information to optimize the plan. But why does using the locally declared variables change this? Why does that delay the creation of the execution plan? Is that actually what's happening? If so, is there a way to force delayed compilation (if that indeed is what's going on here) even when not using local variables in this way? More generally, does anyone have sources on when the execution plan is created for each step of a stored procedure? Googling hasn't provided any helpful information, but I don't think I'm looking for the right thing. Or is my theory just completely unfounded? Edit: Since posting, I've learned of parameter sniffing, and I assume this is what's causing the execution plan to compile prematurely (unless stored procedures indeed compile all at once), so my question remains -- can you force the delay? Or disable the sniffing entirely? The question is academic, since I can force a more efficient plan by replacing the select * from aGiantTable with select * from (select * from aGiantTable where ID in (select ID from #smallTable)) as aGiantTable Or just sucking it up and masking the parameters, but still, this inconsistency has me pretty curious.

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• Acceessing some aggregate functions in a linq datasource in a GridView

  - by Stephen Pellicer

  I am working on a traditional WebForms project. In the project I am trying out some Linq datasources with plans to eventually migrate to an MVC architecture. I am still very new to Linq. I have a GridView using a Linq datasource. The entities I am showing has a to many relationship and I would like to get the maximum value of a column in the many side of the relationship. I can show properties of the base entity in the gridview: <asp:TemplateField HeaderText="Number" SortExpression="tJobBase.tJob.JobNumber"> <ItemTemplate> <asp:Label ID="Label1" runat="server" Text='<%# Bind("tJobBase.tJob.JobNumber") %>'> </asp:Label> </ItemTemplate> </asp:TemplateField> I can also show the count of the many related property: <asp:TemplateField HeaderText="Number" SortExpression="tJobBase.tJob.tHourlies.Count"> <ItemTemplate> <asp:Label ID="Label1" runat="server" Text='<%# Bind("tJobBase.tJob.tHourlies.Count") %>'> </asp:Label> </ItemTemplate> </asp:TemplateField> Is there a way to get the max value of a column called WeekEnding in the tHourlies collection to show in the GridView?

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• Call method immediately after object construction in LINQ query

  - by Steffen

  I've got some objects which implement this interface: public interface IRow { void Fill(DataRow dr); } Usually when I select something out of db, I go: public IEnumerable<IRow> SelectSomeRows { DataTable table = GetTableFromDatabase(); foreach (DataRow dr in table.Rows) { IRow row = new MySQLRow(); // Disregard the MySQLRow type, it's not important row.Fill(dr); yield return row; } } Now with .Net 4, I'd like to use AsParallel, and thus LINQ. I've done some testing on it, and it speeds up things alot (IRow.Fill uses Reflection, so it's hard on the CPU) Anyway my problem is, how do I go about creating a LINQ query, which calls Fills as part of the query, so it's properly parallelized? For testing performance I created a constructor which took the DataRow as argument, however I'd really love to avoid this if somehow possible. With the constructor in place, it's obviously simple enough: public IEnumerable<IRow> SelectSomeRowsParallel { DataTable table = GetTableFromDatabase(); return from DataRow dr in table.Rows.AsParallel() select new MySQLRow(dr); } However like I said, I'd really love to be able to just stuff my Fill method into the LINQ query, and thus not need the constructor overload.

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• Creating a Linq->HQL provider

  - by Mike Q

  Hi all, I have a client application that connects to a server. The server uses hibernate for persistence and querying so it has a set of annotated hibernate objects for persistence. The client sends HQL queries to the server and gets responses back. The client has an auto-generated set of objects that match the server hibernate objects for query results and basic persistence. I would like to support using Linq to query as well as Hql as it makes the queries typesafe and quicker to build (no more typos in HQL string queries). I've looked around at the following but I can't see how to get them to fit with what I have. NHibernate's Linq provider - requires using NHibernate ISession and ISessionFactory, which I don't have LinqExtender - requires a lot of annotations on the objects and extending a base type, too invasive What I really want is something that will generate give me a nice easy to process structure to build the HQL queries from. I've read most of a 15 page article written by one of the C# developers on how to create custom providers and it's pretty fraught, mainly because of the complexity of the expression tree. Can anyone suggest an approach for implementing Linq - HQL translation? Perhaps a library that will the cleanup of the expression tree into something more SQL/HQLish. I would like to support select/from/where/group by/order by/joins. Not too worried about subqueries.

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• LINQ query to find if items in a list are contained in another list

  - by cjohns

  I have the following code: List<string> test1 = new List<string> { "@bob.com", "@tom.com" }; List<string> test2 = new List<string> { "[email protected]", "[email protected]" }; I need to remove anyone in test2 that has @bob.com or @tom.com. What I have tried is this: bool bContained1 = test1.Contains(test2); bool bContained2 = test2.Contains(test1); bContained1 = false but bContained2 = true. I would prefer not to loop through each list but instead use a Linq query to retrieve the data. bContained1 is the same condition for the Linq query that I have created below: List<string> test3 = test1.Where(w => !test2.Contains(w)).ToList(); The query above works on an exact match but not partial matches. I have looked at other queries but I can find a close comparison to this with Linq. Any ideas or anywhere you can point me to would be a great help.

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• SQL - date variable isn't being parsed correctly?

  - by Bill Sambrone

  I am pulling a list of invoices filtered by a starting and ending date, and further filtered by type of invoice from a SQL table. When I specify a range of 2013-07-01 through 2013-09-30 I am receiving 2 invoices per company when I expect 3. When I use the built in select top 1000 query in SSMS and add my date filters, all the expected invoices appear. Here is my fancy query that I'm using that utilizing variables that are fed in: DECLARE @ReportStart datetime DECLARE @ReportStop datetime SET @ReportStart = '2013-07-01' SET @ReportStop = '2013-09-30' SELECT Entity_Company.CompanyName, Reporting_AgreementTypes.Description, Reporting_Invoices.InvoiceAmount, ISNULL(Reporting_ProductCost.ProductCost,0), (Reporting_Invoices.InvoiceAmount - ISNULL(Reporting_ProductCost.ProductCost,0)), (Reporting_AgreementTypes.Description + Entity_Company.CompanyName), Reporting_Invoices.InvoiceDate FROM Reporting_Invoices JOIN Entity_Company ON Entity_Company.ClientID = Reporting_Invoices.ClientID LEFT JOIN Reporting_ProductCost ON Reporting_ProductCost.InvoiceNumber =Reporting_Invoices.InvoiceNumber JOIN Reporting_AgreementTypes ON Reporting_AgreementTypes.AgreementTypeID = Reporting_Invoices.AgreementTypeID WHERE Reporting_Invoices.AgreementTypeID = (SELECT AgreementTypeID FROM Reporting_AgreementTypes WHERE Description = 'Resold Services') AND Reporting_Invoices.InvoiceDate >= @ReportStart AND Reporting_Invoices.InvoiceDate <= @ReportStop ORDER BY CompanyName,InvoiceDate The above only returns 2 invoices per company. When I run a much more basic query through SSMS I get 3 as expected, which looks like: SELECT TOP 1000 [InvoiceID] ,[AgreementID] ,[AgreementTypeID] ,[InvoiceDate] ,[Comment] ,[InvoiceAmount] ,[InvoiceNumber] ,[TicketID] ,Entity_Company.CompanyName FROM Reporting_Invoices JOIN Entity_Company ON Entity_Company.ClientID = Reporting_Invoices.ClientID WHERE Entity_Company.ClientID = '9' AND AgreementTypeID = (SELECT AgreementTypeID FROM Reporting_AgreementTypes WHERE Description = 'Resold Services') AND Reporting_Invoices.InvoiceDate >= '2013-07-01' AND Reporting_Invoices.InvoiceDate <= '2013-09-30' ORDER BY InvoiceDate DESC I've tried stripping down the 1st query to include only a client ID on the original invoice table, the invoice date, and nothing else. Still only get 2 invoices instead of the expected 3. I've also tried manually entering the dates instead of the @ variables, same result. I confirmed that InvoiceDate is defined as a datetime in the table. I've tried making all JOIN's a FULL JOIN to see if anything is hiding, but no change. Here is how I stripped down the original query to keep all other tables out of the mix and yet I'm still getting only 2 invoices per client ID instead of 3 (I manually entered the ID for the type filter): --DECLARE @ReportStart datetime --DECLARE @ReportStop datetime --SET @ReportStart = '2013-07-01' --SET @ReportStop = '2013-09-30' SELECT --Entity_Company.CompanyName, --Reporting_AgreementTypes.Description, Reporting_Invoices.ClientID, Reporting_Invoices.InvoiceAmount, --ISNULL(Reporting_ProductCost.ProductCost,0), --(Reporting_Invoices.InvoiceAmount - ISNULL(Reporting_ProductCost.ProductCost,0)), --(Reporting_AgreementTypes.Description + Entity_Company.CompanyName), Reporting_Invoices.InvoiceDate FROM Reporting_Invoices --JOIN Entity_Company ON Entity_Company.ClientID = Reporting_Invoices.ClientID --LEFT JOIN Reporting_ProductCost ON Reporting_ProductCost.InvoiceNumber = Reporting_Invoices.InvoiceNumber --JOIN Reporting_AgreementTypes ON Reporting_AgreementTypes.AgreementTypeID = Reporting_Invoices.AgreementTypeID WHERE Reporting_Invoices.AgreementTypeID = '22'-- (SELECT AgreementTypeID FROM Reporting_AgreementTypes WHERE Description = 'Resold Services') AND Reporting_Invoices.InvoiceDate >= '2013-07-01' AND Reporting_Invoices.InvoiceDate <= '2013-09-30' ORDER BY ClientID,InvoiceDate This strikes me as really weird as it is pretty much the same query as the SSMS generated one that returns correct results. What am I overlooking? UPDATE I've further refined my "test query" that is returning only 2 invoices per company to help troubleshoot this. Below is the query and a relevant subset of data for 1 company from the appropriate tables: SELECT Reporting_Invoices.ClientID, Reporting_AgreementTypes.Description, Reporting_Invoices.InvoiceAmount, Reporting_Invoices.InvoiceDate FROM Reporting_Invoices JOIN Reporting_AgreementTypes ON Reporting_AgreementTypes.AgreementTypeID = Reporting_Invoices.AgreementTypeID WHERE Reporting_Invoices.AgreementTypeID = (SELECT AgreementTypeID FROM Reporting_AgreementTypes WHERE Description = 'Resold Services') AND Reporting_Invoices.InvoiceDate >= '2013-07-01T00:00:00' AND Reporting_Invoices.InvoiceDate <= '2013-09-30T00:00:00' ORDER BY Reporting_Invoices.ClientID,InvoiceDate The above only returns 2 invoices. Here is the relevant table data: Relevant data from Reporting_AgreementTypes AgreementTypeID Description 22 Resold Services Relevant data from Reporting_Invoices InvoiceID ClientID AgreementID AgreementTypeID InvoiceDate 16111 9 757 22 2013-09-30 00:00:00.000 15790 9 757 22 2013-08-30 00:00:00.000 15517 9 757 22 2013-07-31 00:00:00.000 Actual results from my new modified query ClientID Description InvoiceAmount InvoiceDate 9 Resold Services 3513.79 7/31/13 00:00:00 9 Resold Services 3570.49 8/30/13 00:00:00

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• "Most popular" GROUP BY in LINQ?

  - by tags2k

  Assuming a table of tags like the stackoverflow question tags: TagID (bigint), QuestionID (bigint), Tag (varchar) What is the most efficient way to get the 25 most used tags using LINQ? In SQL, a simple GROUP BY will do: SELECT Tag, COUNT(Tag) FROM Tags GROUP BY Tag I've written some LINQ that works: var groups = from t in DataContext.Tags group t by t.Tag into g select new { Tag = g.Key, Frequency = g.Count() }; return groups.OrderByDescending(g => g.Frequency).Take(25); Like, really? Isn't this mega-verbose? The sad thing is that I'm doing this to save a massive number of queries, as my Tag objects already contain a Frequency property that would otherwise need to check back with the database for every Tag if I actually used the property. So I then parse these anonymous types back into Tag objects: groups.OrderByDescending(g => g.Frequency).Take(25).ToList().ForEach(t => tags.Add(new Tag() { Tag = t.Tag, Frequency = t.Frequency })); I'm a LINQ newbie, and this doesn't seem right. Please show me how it's really done.

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• fastest way to check to see if a certain index in a linq statement is null

  - by tehdoommarine

  Basic Details I have a linq statement that grabs some records from a database and puts them in a System.Linq.Enumerable: var someRecords = someRepoAttachedToDatabase.Where(p=>true); Suppose this grabs tons (25k+) of records, and i need to perform operations on all of them. to speed things up, I have to decided to use paging and perform the operations needed in blocks of 100 instead of all of the records at the same time. The Question The line in question is the line where I count the number of records in the subset to see if we are on the last page; if the number of records in subset is less than the size of paging - then that means there are no more records left. What I would like to know is what is the fastest way to do this? Code in Question int pageSize = 100; bool moreData = true; int currentPage = 1; while (moreData) { var subsetOfRecords = someRecords.Skip((currentPage - 1) * pageSize).Take(pageSize); //this is also a System.Linq.Enumerable if (subsetOfRecords.Count() < pageSize){ moreData = false;} //line in question //do stuff to records in subset currentPage++; } Things I Have Considered subsetOfRecords.Count() < pageSize subsetOfRecords.ElementAt(pageSize - 1) == null (causes out of bounds exception - can catch exception and set moreData to false there) Converting subsetOfRecords to an array (converting someRecords to an array will not work due to the way subsetOfRecords is declared - but I am open to changing it) I'm sure there are plenty of other ideas that I have missed.

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