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• Implementing a 'many-to-many' database

  - by Raven Dreamer

  Greetings, stack*overflow* In my database, I already have one table, 'contacts' that contains records of individual people. I also have several other tables in my database which represent "skill sets" that contain records denoting a particular skill. 1) Am I correct in plotting this as a "many-to-many" relationship? (each contact can have multiple skill sets, and each skill set can belong to multiple contacts) 2) I'm new to databases -- do I want to link the tables? 3) Is there a way to implement this in my program (C# + windows forms) such that for any given record in the 'contacts' table, either the names of all associated 'skill set' tables or all the 'skill' records associated with the 'contact' record could be retrieved? (Database is located on SQL Server Express 2008)

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• LINQ to Entites: How should I handle System.InvalidOperationException when checking for existance of

  - by chris

  I have a many-to-one relationship that users can edit via checkboxes. PK of Foo is ID, and fid contains the id from the checkbox. I'm checking to see if an element exists with: Foo ent; try { ent = ctx.Foo.First(f => f.ID == fid); } catch (System.InvalidOperationException ioe) { ent = new Foo(); } It seems to me that I should be able to do this without throwing an exception. What would be the best way to do this?

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• 'Recursive' LINQ calls

  - by Sir Psycho

  Hi, I'm trying to build an XML tree of some data with a parent child relationship, but in the same table. The two fields of importance are CompetitionID ParentCompetitionID Some data might be CompetitionID=1, ParentCompetitionID=null CompetitionID=2, ParentCompetitionID=1 CompetitionID=3, ParentCompetitionID=1 The broken query I have simply displays results in a flat format. Seeing that I'm working with XML, some sort of recursive functionality is required. I can do this using recursion, but would like to see the linq version. Any help appreciated. var results = from c1 in comps select new { c.CompetitionID, SubComps= from sc in comps.Where (c2 => c2.CompetitionID == c1.CompetitionID) select sc };

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• Rails object inheritence with belongs_to

  - by Rabbott

  I have a simple has_many/belongs_to relationship between Report and Chart. The issue I'm having is that my Chart model is a parent that has children. So in my Report model I have class Report < ActiveRecord::Base has_many :charts end And my Chart model is a parent, where Pie, Line, Bar all inherit from Chart. I'm not sure where the belongs_to :report belongs within the chart model, or children of chart model. I get errors when I attempt to access chart.report because the object is of type "Class" undefined local variable or method `report' for #< Class:0x104974b90 The Chart model uses STI so its pulling say.. 'Pie' from the chart_type column in the charts table.. what am I missing?

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• Cakephp, Retreive Data for HABTM Models using conditional find

  - by ion

  There are 2 Models: Project & Category that are bind with HABTM relationship. I would like to perform a search from projects controller that can do the following: FIND all DISTINCT Project.scedule WHERE Category.slug != 'uncategorised' Apologies for the syntax, I'm no sequel expert. What I have managed to do is to retrieve all projects that do not belong to Category uncategorised into an array however I'm not sure as to how to search again the array result for DISTINCT Project.schedule values (needed to fill out a form drop down) I hope I made myself clear.

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• AutoMapper: How to transform object graph to into?

  - by epitka

  If I have a one-to-many relationship and I want to transorm this into a list of flat Dto-s where some attributes of parent and some of child appear in a dto, is this something that is supported out-of-box with AutoMapper? For example if I have something like this Parent 1. ParentId 2. ParentAttr1 3. List<Child> Child 1. ChildId 2. ChildAttr1 2. ChildAttr2 Dto 1. ParentId 2. ChildId 2. ChildAttr1 3. ChildAttr2 How do I project Parent into a Dto where for each child in parent I will get an instace of Dto? I've setup two maps Parent-Dto and Child-Dto but just doing _mapper.Map(parentInstance) only projects parents attributes. Does this have to be done in two steps, where I would iterate children myself?

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• After C++ - Python or Java?

  - by carleeto

  I'm fast approaching the point in my coding where I would like to quickly write object oriented code in languages other than C++ for a variety of reasons. After a lot of research, my choices have pretty much narrowed down to Python and Java. I'm leaning towards Python because of its relationship to C, but with Java, from what I can see, I get a good introduction to using and creating test suites with Eclipse - there is also Processing which is pulling me towards Java. I'm not the kind of guy to tackle two languages at once, so which one would you recommend and why? What I want at the end is to have an additional language I can use for rapid development. Ease of learning isn't important to me as I'm willing to put in the time regardless. Ability to use the new language widely is.

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• Offer me an ASP.NET & a SQL Server 2008 server specifications for about 2000 concurrent users, please.

  - by amkh

  We have a web application project wich will be created using ASP.NET 4.0, Entity Framework, and SQL Sever 2008 R2. To meet the needs, suppose a normal page of this application that has a query which it takes 10 miliseconds to response on a Core2 Quad @ 2.8GHz proccessor with 2x2GB of DDR3 Ram (EntityFramework overheads are considered). And we will have about 2000 concurrent user at peek times. So, what is the best recommended specifications (CPU/RAM/RAID/...) for the server which will be host this application? -- Or -- How can I calculate that?

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• Hibernate one-to-one: getId() without fetching entire object

  - by Rob

  I want to fetch the id of a one-to-one relationship without loading the entire object. I thought I could do this using lazy loading as follows: class Foo { @OneToOne(fetch = FetchType.LAZY, optional = false) private Bar bar; } Foo f = session.get(Foo.class, fooId); // Hibernate fetches Foo f.getBar(); // Hibernate fetches full Bar object f.getBar().getId(); // No further fetch, returns id I want f.getBar() to not trigger another fetch. I want hibernate to give me a proxy object that allows me to call .getId() without actually fetching the Bar object. What am I doing wrong?

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• How Do I Update a Table From Another Table Only If the Result Count is 1?

  - by Russ Bradberry

  I have a table of 2 tables in a one to many relationship. I want to run an update script that will update the table with the FK of the related table only if there is one result (because if there is multiple then we need to decide which one to use, in another method) Here is what I have so far: UPDATE import_hourly_event_reports i SET i.banner_id = b.banner_id FROM banner b JOIN plan p ON b.plan_id = p.id WHERE b.campain_id = i.campaign_id AND b.size_id = i.size_id AND p.site_id = i.site_id HAVING COUNT(b.banner_id) = 1 As you can see, the HAVING clause doesn't quite work as I'd expect it. I only want to update the row in the import table with the id of the banner from the banner table if the count is equal to 1.

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• Manually Building a Tree in CakePHP

  - by mabwi

  I'm currently working on building an application in CakePHP. There's a quite extensive existing data set that's conceptually a tree, but wasn't previously stored as one. What I mean by that, is there's no real relationship defined in the data. The problem I'm having is getting it to work correctly with the CakePHP tree behaviour. Because I have to set all the values on existing data - as opposed to Cake setting up the structure as elements are inserted - I need to understand how the lft/rght values work. So, I guess the question is: How does the structure data work, specifically the lft/rght values? How do I set it up so that the data comes out rationally, without inserting them one at a time? It's a 2 level tree, with Sections and sub-sections. Thanks for the help

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• nsfetchedresultscontroller with empty sections

  - by WearyMonkey

  I have a database of People and pets, with a one to many relationship Person Pet Name Name Pet <----- Owner I am using a UITableView backed by Core data and a nsfetchedresultscontroller to display the list of pets, grouped into sections by the owner. NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; fetchRequest.entity = [NSEntityDescription entityFromName:@"Pet" inManagedObjectContext:context] NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"Owner.name" ascending:YES]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; NSFetchedResultsController *controller = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:context sectionNameKeyPath:@"Owner.name" cacheName:@"Root"]; This works to display all pets under their owners section, however I also want to display the empty sections of People who do not have any pets? Is this possible? Thanks for any help.

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• Circular Reference for Parent Link on Work Item cannot be resolved by Retry

  - by Atters

  I receive the following error; OH-TFS-Connector-0051: Operation failed getCollectionMetaData. Server Error : TF201063: Adding a Parent link to work item 1737 would result in a circular relationship. To create this link, evaluate the existing links, and remove one of the other links in the cycle. I have completely flattened out the Work Items in the source project. When retrying the migration the timestamp is modified on the pending errors however the issues are not resolved. These Work Items now have no parents or children in the source project. So I'm wondering if the retry list is no longer valid but there doesn't appear to be a away to have it update? I can run the whole migration again, however it takes 5-7 hours to just do the work items so it would be great if there is a quick fix.

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• Want to save data field from form into two columns of two models.

  - by vette982

  I have a Profile model with a hasOne relationship to a Detail model. I have a registration form that saves data into both model's tables, but I want the username field from the profile model to be copied over to the usernamefield in the details model so that each has the same username. function new_account() { if(!empty($this->data)) { $this->Profile->modified = date("Y-m-d H:i:s"); if($this->Profile->save($this->data)) { $this->data['Detail']['profile_id'] = $this->Profile->id; $this->data['Detail']['username'] = $this->Profile->username; $this->Profile->Detail->save($this->data); $this->Session->setFlash('Your registration was successful.'); $this->redirect(array('action'=>'index')); } } } This code in my Profile controller gives me the error: Undefined property: Profile::$username Any ideas?

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• save object associate to another object automatically

  - by Luca Romagnoli

  Hi i have these classes: class Core < ActiveRecord::Base belongs_to :resource, :polymorphic => true belongs_to :image, :class_name => 'Multimedia', :foreign_key => 'image_id' end class Place < ActiveRecord::Base has_one :core, :as => :resource end If i try do launch this: a = Place.find(5) a.name ="a" a.core.image_id = 24 a.save name is saved. image_id no i want save automatically all changes in records in relationship with place class at a.save command. is possible? thanks

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• Best practice in Rails when editing scaffold made pages

  - by abegbg

  I have a best practice question. I have two classes, company and category. They have a many-to-many relationship. When clicking a category I shall go to a page showing all companies with the chosen category. Pretty straight forward. My question is: Should I list all the companies on the companies/index.html.erb after filtering the companies in the controller? or Should I list all the companies on the categories/show.html.erb page? or Should I do a completely new page, since it doesn't really fit into any of the two above? Do you generally make a new page when your goal doesn't fit the scaffold made pages or do you use them quite freely? I am working/learning alone with rails, so there are a lot of best practice questions popping up all the time. Cheers Carl

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• Rails - Why is my custom validation being triggered for only a build command.

  - by adam

  I have a sentence and correction model with a has_one and belongs_to relationship respectively. For some reason when I do def create @sentence = Sentence.find(params[:sentence_id]) @correction = @sentence.build_correction(params[:correction]) a custom validation I wrote for Correction is being called at the build_correction point. the validation is below class Correction < ActiveRecord::Base attr_accessible :text, :sentence_id, :user_id belongs_to :sentence belongs_to :user validate :correction_is_different_than_sentence def correction_is_different_than_sentence errors.add(:text, "can't be the same as the original sentence.") if (text == self.sentence.text) end the problem is for some reason on validation the correction object doesn't have the sentence id set (despite I used the build_correction method) and so it complains "you have nil object .... while executing nil.text" in the if clause in the validation above. So my question is why is the validation occuring for a build command, i thought it only triggers on a create or update. And why isnt the sentence_id getting set?

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• What is your approach to draw a representation of your network ?

  - by Kartoch

  Hello, I'm looking to the community to see how people are drawing their networks, i.e. using symbols to represent complex topology. You can have hardware approach, where every hardware unit are represented. You can also have "entity" approach, where each "service" is shown. Both are interesting but it is difficult to have both on the same schema (but this is needed, especially using virtualization environment). Furthermore, it is difficult to have complex informations on such representation. For instance security parameters (encrypted link, need for authentication) or specific details (protocol type, ports, encapsulation). So my question is: where your are drawing a representation of your network, what is your approach ? Are you using methodology and/or specific softwares ? What is your recommendations for information to put (or not) ? How to deal with the complexity when the network becomes large and/or you want to put a lot of information on it ? Examples and links to good references will be appreciated.

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• FileInputStream and FileOutputStream to the same file: Is a read() guaranteed to see all write()s that "happened before"?

  - by user946850

  I am using a file as a cache for big data. One thread writes to it sequentially, another thread reads it sequentially. Can I be sure that all data that has been written (by write()) in one thread can be read() from another thread, assuming a proper "happens-before" relationship in terms of the Java memory model? Is this behavior documented? EDIT: In my JDK, FileOutputSream does not override flush(), and OutputStream.flush() is empty. That's why I'm wondering... EDIT^2: The streams in question are owned exclusively by a class that I have full control of. Each stream is guaranteed to be accesses by one thread only. My tests show that it works as expected, but I'm still wondering if this is guaranteed and documented. See also this related discussion: http://chat.stackoverflow.com/rooms/17598/discussion-between-hussain-al-mutawa-and-user946850

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• has_many conditions

  - by user305270

  c = "(f.profile_id = #{self.id} OR f.friend_id = #{self.id})" c += AND + "(CASE WHEN f.profile_id=#{self.id} THEN f.friend_id ELSE f.profile_id END = p.id)" c += AND + "(CASE WHEN f.profile_id=#{self.id} THEN f.profile_rejected ELSE f.friend_rejected END = 1)" c += AND + "(p.banned = 0)" I need this to be used in a has_many relationship like this: has_many :removed_friends, :conditions => ??? how do i set there the self.id?, or how do i pass there the id? Then i want to use the will_paginate plugin: @profile.removed_friends.paginate(:page => 1, :per_page => 20) Thanks for your help

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• Storing Data as XML BLOB

  - by NBrowne

  Hi, At the moment the team i am working with is looking into the possibility of storing data which is entered by users from a series of input wizard screens as an XML blob in the database. the main reason for this being that i would like to write the input wizard as a component which can be brought into a number of systems without having to bring with it a large table structure. To try to clarify if the wizard has 100 input fields (for example) then if i go with the normal relational db structure then their will be a 1 to 1 relationship so will have 100 columns in database. So to get this working in another system will have to bring the tables,strore procedures etc into the new system. I have a number of reservations about this but i would like peoples opinions?? thanks

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• how do I integrate the aspnet_users table that comes with asp.net membership into my existing databa

  - by ooo

  i have a database that already has a users table COLUMNS: userID - int loginName - string First - string Last - string i just installed the asp.net membership table. Right now all of my tables are joined into my users table foreign keyed into the "userId" field How do i integrate asp.net_users table into my schema? here are the ideas i thought of: Add a membership_id field to my users table and on new inserts, include that new field in my users table. This seems like the cleanest way as i dont need to break any existing relationships. break all existing relationship and move all of the fields in my user table into the asp.net_users table. This seems like a pain but ultimately will lead to the most simple, normalized solution any thoughts?

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• Rails: Best practice to store user settings?

  - by ole_berlin

  Hi, I'm wondering what the best way is to store user settings? For a web 2.0 app I want users to be able to select certain settings. At the moment is it only when to receive email notifications. The easiest way would be to just create a Model "Settings" and have a column for every setting and then have a 1-1 relationship with users. But is there a pattern to solve this better? Is it maybe better to store the info in the user table itself? Or should I use a table with "settings_name" and "settings_value" to be completely open about the type of settings stored there (without having to run any migrations when adding options)? What is your opinion? Thanks

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• I never really understood: what is Application Binary Interface (ABI)?

  - by claws

  I never clearly understood what is an ABI. I'm sorry for such a lengthy question. I just want to clearly understand things. Please don't point me to wiki article, If could understand it, I wouldn't be here posting such a lengthy post. This is my mindset about different interfaces: TV remote is an interface between user and TV. It is an existing entity but useless (doesn't provide any functionality) by itself. All the functionality for each of those buttons on the remote is implemented in the Television set. Interface: It is a "existing entity" layer between the functionality and consumer of that functionality. An, interface by itself is doesn't do anything. It just invokes the functionality lying behind. Now depending on who the user is there are different type of interfaces. Command Line Interface(CLI) commands are the existing entities, consumer is the user and functionality lies behind. functionality: my software functionality which solves some purpose to which we are describing this interface. existing entities: commands consumer: user Graphical User Interface(GUI) window,buttons etc.. are the existing entities, again consumer is the user and functionality lies behind. functionality: my software functionality which solves some purpose to which we are describing this interface. existing entities: window,buttons etc.. consumer: user Application Programming Interface(API) functions or to be more correct, interfaces (in interfaced based programming) are the existing entities, consumer here is another program not a user. and again functionality lies behind this layer. functionality: my software functionality which solves some purpose to which we are describing this interface. existing entities: functions, Interfaces(array of functions). consumer: another program/application. Application Binary Interface (ABI) Here is my problem starts. functionality: ??? existing entities: ??? consumer: ??? I've wrote few softwares in different languages and provided different kind of interfaces (CLI, GUI, API) but I'm not sure, if I ever, provided any ABI. http://en.wikipedia.org/wiki/Application_binary_interface says: ABIs cover details such as data type, size, and alignment; the calling convention, which controls how functions' arguments are passed and return values retrieved; the system call numbers and how an application should make system calls to the operating system; Other ABIs standardize details such as the C++ name mangling,[2] . exception propagation,[3] and calling convention between compilers on the same platform, but do not require cross-platform compatibility. Who needs these details? Please don't say, OS. I know assembly programming. I know how linking & loading works. I know what exactly happens inside. Where did C++ name mangling come in between? I thought we are talking at the binary level. Where did languages come in between? anyway, I've downloaded the [PDF] System V Application Binary Interface Edition 4.1 (1997-03-18) to see what exactly it contains. Well, most of it didn't make any sense. Why does it contain 2 chapters (4th & 5th) which describe the ELF file format.Infact, these are the only 2 significant chapters that specification. Rest of all the chapters "Processor Specific". Anyway, I thought that it is completely different topic. Please don't say that ELF file format specs are the ABI. It doesn't qualify to be Interface according to the definition. I know, since we are talking at such low level it must be very specific. But I'm not sure how is it "Instruction Set Architecture(ISA)" specific? Where can I find MS Window's ABI? So, these are the major queries that are bugging me.

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• UML binary association aggregatee has access to aggregator

  - by user314172

  Firstly, I'd like to thank those who answered my previous question ages ago. Currently I'm engaging more in the design phase UMLs, as this is my first medium scale deployment I'm entrusted with. This is extremely simple, but it bugs me so. If (Component) owns (Manager of Component), and (Manager of Component) has a reference to (Component) through which it manages it; how do you fully describe the relationship? I know it is aggregative, but how do you describe (Manager of Component) possessing a reference/pointer to the (Component) that physically owns the (Manager of Component) ? Example: Lidar owns a LidarManager

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