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• MySQL Join Comma Separated Field

  - by neeraj

  I have two tables. First Table is a batch table that contain comma separated student id in field "batch" batch -------------- id batch -------------- 1 1,2 2 3,4 Second Table is marks marks ---------------------- id studentid subject marks 1 1 English 50 2 2 English 40 3 3 English 70 4 1 Math 65 5 4 English 66 6 5 English 75 7 2 Math 55 How we can find those students of first batch id =1 who have scored more than 45 marks in English without using sub query. Problem i found to get this done using a single query is that we can not use IN as an association operator in JOIN statement What changes are required in below query to make it work? SELECT * FROM batch INNER JOIN marks ON marks.studentid IN(batch.batch) where batch.id = 1

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• MS SQL 2005 - Understanding ouput of DBCC SHOWCONTIG

  - by user169743

  I'm seeing some slow performance on a MS SQL 2005 database. I've been doing some research regarding MS SQL performance but I'm having difficulty fully understanding the output of SHOWCONTIG and would be very grateful if someone could have a look and offer some suggestions to improve performance. TABLE level scan performed. Pages Scanned................................: 19348 Extents Scanned..............................: 2427 Extent Switches..............................: 3829 Avg. Pages per Extent........................: 8.0 Scan Density [Best Count:Actual Count].......: 63.16% [2419:3830] Logical Scan Fragmentation ..................: 8.40% Extent Scan Fragmentation ...................: 35.15% Avg. Bytes Free per Page.....................: 938.1 Avg. Page Density (full).....................: 88.41%

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• Storing expression template functors

  - by UncaughtException

  Hello guys, at the moment I'm really interested in expression templates and want to code a library for writing and differentiating mathematical functions with a lambda-style syntax. At the moment, I'm able to write (_x * _x)(2); and get the correct result 4. But I would really like to do something like MathFunction f = _x * _x; f(2);, but I don't have any ideas on how to cope with the recursive expression templates on the right side. Is it possible to achieve this without using the 'auto'-Keyword instead of MathFunction or having to make the operator() virtual? Thanks for your help!

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• Pitfalls when converting C++/CLI to C++

  - by directedition

  I have a library written in C++/CLI and I want to open it up. I want it to be as cross-platform as possible and be able to write bindings to it for other languages to use (Java, Python, etc, etc). To do this, the library needs to be in plain C++ for maximum flexibility. I figure that the logical structures are already there, I just need to replace the .NET libraries it uses with the standard C++ ones. Is this a misguided notion? What should I watch out for when making this transition?

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• Converting a PHP array to class variables.

  - by animuson

  Simple question, how do I convert an associative array to variables in a class? I know there is casting to do an (object) $myarray or whatever it is, but that will create a new stdClass and doesn't help me much. Are there any easy one or two line methods to make each $key => $value pair in my array into a $key = $value variable for my class? I don't find it very logical to use a foreach loop for this, I'd be better off just converting it to a stdClass and storing that in a variable, wouldn't I? class MyClass { var $myvar; // I want variables like this, so they can be references as $this->myvar function __construct($myarray) { // a function to put my array into variables } }

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• Where to reopen a class in RoR

  - by Jeriko

  I'm attempting to reopen the String class in rails and add a bunch more methods for my app to use. Writing the code isn't a problem - my question is rather about where this code should go. It doesn't make sense to me to reopen a class inside a different model file, because it really has nothing to do with any of the models specifically. I thought perhaps somewhere in config or lib would make sense, but I'm not particularly well versed with RoR yet. To summarize, where would be the most logical place to define class-modifying code?

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• C# Elegant way to handle checking for an item in a collection.

  - by JL

  I've posted a code sample below. Firstly let me explain termStore.Groups in the code below is a collection of Group Objects (The exact class is irrelevant). Checking for null : if (termStore.Groups[groupName] == null) seems like a logical (clean) approach, but if the Groups collection is empty then an exception is produced. using the termStore.Groups.Contains is not an option either because this expects a strong type i.e: .Contains(Group)... not .Contains(GroupName as string) Can someone recommend a clean / generic way I can check for if an item exists in collection . Thank you.... TermStore termStore = session.TermStores.Where(ts => ts.Name == termStoreName).FirstOrDefault(); if (termStore.Groups[groupName] == null) { termStore.CreateGroup(groupName); termStore.CommitAll(); } Update: The exact class Sharepoint Taxonomy Classes. http://msdn.microsoft.com/en-us/library/microsoft.sharepoint.taxonomy.group.aspx

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• Binding in ContentControl Crash

  - by ImJames

  Can anyone tell me why this crashes my app? There seems to be some endless recursion by I can't figure out why. I get this exception Logical tree depth exceeded while traversing the tree. This could indicate a cycle in the tree <ContentControl Content="{Binding}"> <ContentControl.ContentTemplate> <DataTemplate> <Button Content="{Binding MyString}"/> </DataTemplate> </ContentControl.ContentTemplate> </ContentControl> And this is all I have as Source public MainWindow() { InitializeComponent(); MyString = "Test"; this.DataContext = this; } public string MyString { get; set; }

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• Why exactly is calling the destructor for the second time undefined behavior in C++?

  - by sharptooth

  As mentioned in this answer simply calling the destructor for the second time is already undefined behavior 12.4/14(3.8). For example: class Class { public: ~Class() {} }; // somewhere in code: { Class* object = new Class(); object->~Class(); delete object; // UB because at this point the destructor call is attempted again } In this example the class is designed in such a way that the destructor could be called multiple times - no things like double-deletion can happen. The memory is still allocated at the point where delete is called - the first destructor call doesn't call the ::operator delete() to release memory. For example, in Visual C++ 9 the above code looks working. Even C++ definition of UB doesn't directly prohibit things qualified as UB from working. So for the code above to break some implementation and/or platform specifics are required. Why exactly would the above code break and under what conditions?

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• Does any method exist quickly to detect valid range versions of used library

  - by daneel-yaitskov

  I'm a beginner Haskell programmer. I have written some useful code for the last six month. And I want to release a library from it. The code will use system installation cabal as any Haskell library. A library is released with cabal has a meta data file where there is a logical predicate from the libraries and their versions. A developer usually uses one set libraries. It tediously care a set of the sets libraries. How to know either my library is compiled successfully or not for some subset libraries?

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• SQL Server 2005 - Understanding ouput of DBCC SHOWCONTIG

  - by user169743

  I'm seeing some slow performance on a SQL Server 2005 database. I've been doing some research regarding SQL Server performance but I'm having difficulty fully understanding the output of SHOWCONTIG and would be very grateful if someone could have a look and offer some suggestions to improve performance. TABLE level scan performed. Pages Scanned................................: 19348 Extents Scanned..............................: 2427 Extent Switches..............................: 3829 Avg. Pages per Extent........................: 8.0 Scan Density [Best Count:Actual Count].......: 63.16% [2419:3830] Logical Scan Fragmentation ..................: 8.40% Extent Scan Fragmentation ...................: 35.15% Avg. Bytes Free per Page.....................: 938.1 Avg. Page Density (full).....................: 88.41%

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• Auto height and the float issue.

  - by William Hand

  I have had this issue before and can't remember if and how I fixed it. I have to create a scenario where I have 2 DIV's floated left and right inside a parent DIV. The 2 floating DIV's have height:auto, but the parent ignores them (perfectly logical) and the background of the parent DIV can't be seen. I know what the issue is, but are there any suggestions of how to solve it? Or any alternatives, I am willing to try a new approach. Thanks in advance for any help.

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• C++ Word-Number to int

  - by Andrew

  I'm developing a program that makes basic calculations using words instead of numbers. E.g. five + two would output seven. The program becomes more complex, taking input such as two_hundred_one + five_thousand_six (201 + 5006) Through operator overloading methods, I split each number and assign it to it's own array index. two would be [0], hundred is [1], and one is [2]. Then the array recycles for 5006. My problem is, to perform the actual calculation, I need to convert the words stored in the array to actual integers. I have const string arrays such as this as a library of the words: const string units[] = { "", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" }; const string teens[] = { "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen" }; const string tens[] = { "", "", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety" }; If my 'token' array has stored in it two hundred one in index 0, 1, and 2, I'm not sure what the best way to convert these to ints would involve.

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• Should all presentational images be defined in CSS?

  - by Grant Crofton

  I've been learning (X)HTML & CSS recently, and one of the main principles is that HTML is for structure and CSS for presentation. With that in mind, it seems to me that a fair number of images on most sites are just for presentation and as such should be in the CSS (with a div or span to hold them in the HTML) - for example logos, header images, backgrounds. However, while the examples in my book put some images in CSS, they are still often in the HTML. (I'm just talking about 'presentational' images, not 'structural' ones which are a key part of the content, for example photos in a photo site). Should all such images be in CSS? Or are there technical or logical reasons to keep them in the HTML? Thanks, Grant

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• C#: Custom assembly directory

  - by Svish

  Say we have an application which consists of one executable and 5 libraries. Regularly all of these will be contained in one directory and the libraries will be loaded from there. Is it possible to do so that I can have for example some of the libraries in one directory called Lib, and the rest in one called Lib2? So that the application directory would only contain the executable itself and the other assemblies would be contained in various logical directories. How can I do this? And I would like to know how to do the loading of the assemblies, but also how to make the building of the application put the assemblies in the right directory.

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• How to limit the number of post values on UpdatePanel ?

  - by Aristos

  I have notice that the UpdatePanel post every field included on the form on every trigger. But in most of my cases I use 2-3 UpdatePanels at the same page, and each one is independent. When I click for update the one panel, then my page receive all the input data of the page (ok this is logical) but I won to read only this UpdatePanels data and act according, and not the other panels data. So I see that a lot of traffic is happened this way. So is there a way to say to one UpdatePanel - send only my input data, and not everything found on the page. ? Thank you in advanced.

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• Undefined / Uninitialized default values in a class

  - by Jir

  Let's suppose you have this class: class A { public: A () {} A (double val) : m_val(val) {} ~A () {} private: double m_val; }; Once I create an instance of A, how can I check if m_val has been initialized/defined? Put it in other words, is there a way to know if m_val has been initialized/defined or not? Something along the lines of the defined operator in Python, I suppose. (But correct me if I'm wrong.) I thought of modifying the class and the c-tors the following way: class A { public: A () : defined(false) {} A (double val) : m_val(val), defined(true) {} ~A () {} private: double m_val; bool defined; }; How do you rate this solution? Any suggestion? TIA, Chris

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• Documented process for using facebook connect for the iPhone to upload photos

  - by Corey Floyd

  After looking I did come accross this post on the facebook forums: link They are feeding the facebook object a UIImage. That seems logical, but where is this documented? The API documentation is generalized to all platforms. Where are the iPhone specific requirements for arguments and their data types? Thanks **Update***** I still have not came across any API docs pertaining to Cocoa. I did, however, gather the information I needed by piecing together forum information, Facebook sample code, and some glue. Hopefully they'll issue something a little more concrete over the next few months.

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• C++ and preprocessor macro gotcha

  - by aaa

  hello. Appologies for yet another gotcha question. Can you figure out what is wrong with the statement below? gcc error states: "type name declared as function returning array". #define MACRO(a) (a)[1] class index { typedef int index_type[2]; index_type& operator[](int i); }; int k = 0; int i = MACRO(index()[k]); ps: is such questions are deemed too annoying, I am going to stop.

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• Purpose of IF, ELSE, FOR macros ?

  - by psihodelia

  I have a source code of a library which has a lot of strange IF, ELSE, FOR, etc. macros for all common C-keywords instead of using just usual if,else,for,while keywords. These macros are defined like this: #define IF( a) if( increment_if(), a) where increment_if() function is defined so: static __inline void increment_if( void) { // If the "IF" operator comes just after an "ELSE", its counter // must not be incremented. ... //implementation } I don't really understand, what is the purpose of such macros? This library is for a real-time application and I suppose that using such macros must slow-down an application.

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• How to increment a value using a C-Preprocessor?

  - by mystify

  Example: I try to do this: static NSInteger stepNum = 1; #define METHODNAME(i) -(void)step##i #define STEP METHODNAME(stepNum++) @implementation Test STEP { // do stuff... [self nextFrame:@selector(step2) afterDelay:1]; } STEP { // do stuff... [self nextFrame:@selector(step3) afterDelay:1]; } STEP { // do stuff... [self nextFrame:@selector(step4) afterDelay:1]; } // ... When building, Xcode complains that it can't increment stepNum. This seems logical to me, because at this time the code is not "alive" and this pre-processing substitution stuff happens before actually compiling the source code. Is there another way I could have an variable be incremented on every usage of STEP macro, the easy way?

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• What's the deal with all of the abstract stuff?

  - by JustVenting

  I see a lot of talk about MVVM, MVC, Design Patterns etc... You know, some guy has a blog, and he spent the last six months learning about one these things and desiging a program centered around that concept and then he goes on and on about it like its better than sliced bread. I read all of this crap and I wonder, whatever happened to simple logical programming? Not self-absorbed huge frameworks of design patterns and mvc and whatever else you can think of... just simple linear programming, perhaps a few classes to encapsulate things here and there.

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• Glib::ustring and Japanese characters

  - by user294787

  Glib::ustring is supposed to work well with UTF8 but I have a problem when working with Japanese strings. If you compare those two strings, "???" and "???", using == operator or compare method, it will answer that those two strings are equals. I don't understand why. How Glib::ustring works ? The only way I found to get false to the comparison is to compare strings of different sizes. For example "?????" and "????". Very strange...

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• How to automatically check out a database file in a source controlled web application ?

  - by TheRHCP

  Hello, I am working on an ASP.NET web application, we are a small team (4 students) and we do not have access to a dedicated server to host the database instance. So for this web application we decided just to put the database file in the App_Data folder. The problem is that our project is source controled on TFS, so every time you open the solution and try to launch the web application, we get an expcetion saying that database is read-only. That is logical because the databse file is not automatically checked-out. Is there a workaround to avoid a manual check-out of the database file everytime we open the solution ? Thanks.

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• Mixing LINQ to SQL with properties of objects in a generic list

  - by BPotocki

  I am trying to accomplish something like this query: var query = from a in DatabaseTable where listOfObjects.Any(x => x.Id == a.Id) select a; Basically, I want to filter the results where a.Id equals a property of one of the objects in the generic list "listOfObjects". I'm getting the error "Local sequence cannot be used in LINQ to SQL implementation of query operators except the Contains() operator." Any ideas on how to filter this in an easily readable way using "contains" or another method? Thanks in advance.

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