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• Database Modeling - Either/Or in Many-to-Many

  - by EkoostikMartin

  I have an either/or type of situation in a many-to-many relationship I'm trying to model. So I have these tables: Message ---- *MessageID MessageText Employee ---- *EmployeeID EmployeeName Team ---- *TeamID TeamName MessageTarget ---- MessageID EmployeeID (nullable) TeamID (nullable) So, a Message can have either a list of Employees, or a list of Teams as a MessageTarget. Is the MessageTarget table I have above the best way to implement this relationship? What constraints can I place on the MessageTarget effectively? How should I create a primary key on MessageTarget table?

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• How to assign optional attribute of NSManagedObject in a NSManagedObjectModel having Three NSManaged

  - by Kundan

  I am using coredata framework. In my NSManagedObjectModel i am using three entities that are Class, Student and Score where class and student have one-to-many & inverse relationship and Student and Score have also inverse but one-one relationship. Score entity has all optional attributes and having default '0' decimalVaue, which is not assigned at the time new Student is added. But later i want to assign them score individually and also to particular attribute not all of score attributes in a go. I am able to create and add Students to particular Class but dont have any idea how to call particular student and assign them score. For example I want to assign Score'attribute "dribbling" [there are many attributes like "tackling"] a decimal value to Student "David" of Class "Soccer" ,how i can do that? Thanks in advance for any suggestion.

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• Grails GORM on multiple Forms

  - by Fabien Barbier

  Usually I'm using One-to-many relationship by this way : class Subject { static hasMany = [ crfs : Crf ] String name ... } class Crf { String title String info ... } I can extend this relationship to others domains, Ex : static hasMany = [ crfs : Crf, crfb : CrfBlood ...] But in my case I have to link the Subject domain to 30 others domains, maybe more...(ex : CrfBlood, CrfMedical, crfFamily, etc...). What domain model implementation should I use in my case ? I would like to keep the dynamic finders usability in my project.

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• What is the "owning side" in an ORM mapping?

  - by Yousui

  Hi guys, I'm new to JPA. Now I have a question that what exactly is the owning side mean? I only have a rough idea of it. Can someone give me an explanation with some mapping examples(one to many, one to one, many to one) please? Great thanks. ps, the following text is excerpt from the decription of @OneToOne in java EE 6 documentation. You can see the concept owning side in it. Defines a single-valued association to another entity that has one-to-one multiplicity. It is not normally necessary to specify the associated target entity explicitly since it can usually be inferred from the type of the object being referenced. If the relationship is bidirectional, the non-owning side must use the mappedBy element of the OneToOne annotation to specify the relationship field or property of the owning side.

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• In an extension method how do a create an object based on the implementation class

  - by Greg

  Hi, In an extension method how do a create an object based on the implementation class. So in the code below I wanted to add an "AddRelationship" extension method, however I'm not sure how within the extension method I can create an Relationship object? i.e. don't want to tie the extension method to this particular implementation of relationship public static class TopologyExtns { public static void AddNode<T>(this ITopology<T> topIf, INode<T> node) { topIf.Nodes.Add(node.Key, node); } public static INode<T> FindNode<T>(this ITopology<T> topIf, T searchKey) { return topIf.Nodes[searchKey]; } public static bool AddRelationship<T>(this ITopology<T> topIf, INode<T> parentNode, INode<T> childNode) { var rel = new RelationshipImp(); // ** How do I create an object from teh implementation // Add nodes to Relationship // Add relationships to Nodes } } public interface ITopology<T> { //List<INode> Nodes { get; set; } Dictionary<T, INode<T> > Nodes { get; set; } } public interface INode<T> { // Properties List<IRelationship<T>> Relationships { get; set; } T Key { get; } } public interface IRelationship<T> { // Parameters INode<T> Parent { get; set; } INode<T> Child { get; set; } } namespace TopologyLibrary_Client { class RelationshipsImp : IRelationship<string> { public INode<string> Parent { get; set; } public INode<string> Child { get; set; } } } public class TopologyImp<T> : ITopology<T> { public Dictionary<T, INode<T>> Nodes { get; set; } public TopologyImp() { Nodes = new Dictionary<T, INode<T>>(); } } thanks

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• How can I validate XML against an XSD with distinct imports and namespaces?

  - by Pedrolopes

  Hi there!! I am trying to validate a few XML files and I'm failing due to various issues with the XSD definition and the namespaces... This is public info, so no problem sharing data: the main XSD is at http://bioinformatics.ua.pt/euadr/euadr_types.xsd and it imports another XSD at the same location name common_types.xsd, I've validated them in W3C validator, and they passed. The XML <?xml version="1.0"?> <relationship xmlns="http://euadr.biosemantic.erasmusmc.org/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://euadr.biosemantic.erasmusmc.org/ http://bioinformatics.ua.pt/euadr/euadr_types.xsd"> <sourceId> <source>SMILE</source> <code>[S]1(=O)(=O)N(C(</code> </sourceId> <targetId> <source>UP</source> <code>P35354</code> </targetId> <creator>http://cgl.imim.es</creator> <observationDateTime>2010-05-12T19:03:40.097+02:00</observationDateTime> <informationSources> <informationSource> <relationshipType>BINDS</relationshipType> <interaction> <type>pIC50</type> <value>6.55</value> </interaction> <evidence> <type>OBSERVATIONAL</type> <value>1.0</value> </evidence> <databaseIds> <databaseId> <source>PDSP</source> <code> P35354</code> </databaseId> </databaseIds> </informationSource> </informationSources> </relationship> is straightforward and well-formed! I've tested a few online validators, and I'm getting the following error cvc-elt.1: Cannot find the declaration of element 'relationship'. Does anyone has any idea of what the problem is? Is it in the declaration of the namespaces? Of the XSD? Thanks in advance for your help! Cheers!

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• Linq to SQL EntitySet Records causing duplicate insertion

  - by Savvas Sopiadis

  In a WPF application i'm using Linq to SQL in a multi tier application. (This is an archailogy photo filing application), so every excavation has its corresponding Pictures, thus a one-to-many relationship. This relationship is correctly created by SQLMetal (which i'm using to create the POCOs). So here is the situation i 'm having trouble with: Saving changes (either of new or altered objects) is done through UnitOfWork() pattern this way: using (IUnitOfWork unitOfWork = UnitOfWork.Begin()) { //if this is a new record if (SelectedExcavation.excavation.ExcavationId == 0) { IsNewRecord = true; excavService.Add(SelectedExcavation.excavation); } //send the actual changes to the dbms unitOfWork.Commit(); } Everything works fine! BUTTTT!!! Whenever a record gets updated which has (already at least one ) corresponding Picture Record: 1) a new Excavation Record is inserted 2) the current Excavation Record gets updated 3) the previous Picture Record gets its Id changed to the newly created ExcavationId What is going on under the hood? Does Linq to SQL not handle such simple update scenarios? Thanks in advance

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• Core Data and Relationships

  - by alku83

  I have two objects, a Trip and a Place. A Trip represents a journey from one Place to another Place, ie. a Trip needs a fromPlace and a toPlace. So, this is a 1-to-2 relationship, but I need to know which is the "from" and which is the "to". I am not sure how to model this in Core Data. I have created two entities (Trip, Place), and now I want to setup the relationship(s) so I have a fromPlace and a toPlace. Do I need to add an extra field on the Place entity called isFrom, or similar? If this was in a database, I would just have a id column on the Place table, and then two columns in the Trip table - fromPlaceId and toPlaceId. How do I achieve something similar in Core Data?

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• What explains the term orthogonal in a more non-nerd fashion?

  - by dontWatchMyProfile

  For example: Cardinality and optionality are orthogonal properties of a relationship. You can specify that a relationship is optional, even if you have specified upper and/or lower bounds. This means that there do not have to be any objects at the destination, but if there are then the number of objects must lie within the bounds specified. What exactly does "orthogonal" mean? I bet it's just a fancy soundig nerd-style word for something that could be expressed a lot easier to understand for average people ;) From wikipedia: In mathematics, two vectors are orthogonal if they are perpendicular, i.e., they form a right angle. The word comes from the Greek ????? (orthos), meaning "straight", and ????a (gonia), meaning "angle". Anyone?

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• How to execute an Ant task only when source files have been modified?

  - by hughalexb

  There must be an easy way to do this. I build a Flex app using ant that depends on a SWC library, which works fine except that it rebuilds the library whether it needs to or not. How do I tell ant to only run the task if any of the sources files of the library (*.as, *.mxml) are newer than the SWC? I've looked at <dependset but it only seems to delete files, not determine whether a task should be run or not. <depend seems to expect a one-to-one relationship between the source and target files rather than a one-to-many relationship -- I have many input files and one output file, but no intermediate object files. Thanks a lot, Alex

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• View of nodes and their translations

  - by kratib

  I'm trying to create a view of nodes and their translations. Specifically, I want each row to show the node title for each language. The way I'm doing it right now is by filtering the view by a specific language, then adding one relationship of type "Node translation: Translations" for each language on the site. I can then choose the "Node: Title" field, once for the original language and once per relationship. The problem with this approach is that the nodes that don't exist in the filtered language, but exist in other languages, are not included in the view. That's what I need help with.

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• Simulating a belongs_to_many in rails

  - by DavidP6

  I have a situation where in theory I would need to use a belongs_to_many relationship. I have an Example model and a Sentence model. Each example object has one sentence but these sentences are not necessarily unique. So, for example, I could have two example models that each have one sentence that is the same sentence. I'm not sure how to go about doing this in rails. I tried using has_and_belongs_to_many, but ran into problems. It seems that I only need the belongs_to :many part of that relationship. Ideally it would look something like this, but I know there is no belongs_to :many. Example has_one :sentence end Sentence belongs_to_many :examples end

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• How to deal with class composition when components cannot be accessed from the outside?

  - by Chathuranga

  For example if I say I have three classes A, B, and C where B and C have a composition relation ship with A. That means the life of B and C is handled by A, and also B and C cannot access directly from the outside. For some reason my DataService class needs to return objects of B and C as It cant return a object of A as B and C cannot be initialized at the same time. (to be able to initializeC you have to initializeB first). So that I'm returning DataTables from DataService and then inside the class A those data tables are converted to B / C objects. If B and C objects cannot be initialized at the same time is it valid to say that B and C have a composition relationship with A? If its composition is it must to generate A with B and C inside? What is the proper way to handle this sort of a problem? EDIT: Following code explains the way I'm doing it now with DataTables. Example: class A { private List<B> B; private List <C> C; public A() { B= new List<B>(); C= new List<C>(); } public List<B> GetB( DataTable dt) { // Create a B list from dt return B; } } class Presenter { private void Show B() { _View.DataGrid = A.GetB(DataService.GetAListOfB()); } } The actual scenario is I have a class called WageInfo and classes Earning and Deduction having a composition relationship in the design. But for you to generate Deductions first you should Generate earnings and should be saved in a table. Then only you can generate deductions for the earnings to calculate balance wages. Also note that these contained classes have a one to many relationship with the containing class WageInfo. So actually WageInfo has a List<Earnings> and List<Deduction> My initial question was, is it ok if my DataService class returns Deductions / Earnings objects (actually lists) not a WageInfo? Still not clear?

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• Trying to verify understanding of Foreign Keys MSSQL

  - by msarchet

  So I'm working on just a learning project to expose myself to doing some things I do not get to do at work. I'm just making a simple bug and case tracking app (I know there are a million this is just to work with some tools I don't get to). So I was designing my database and realized I've never actually used Foreign Keys before in any of my projects, I've used them before but never actually setting up a column as a FK. So I've designed my database as follows, which I think is close to correct (at least for the initial layout). However When I try to add the FK's to the linking Tables I get an error saying, "The tables present in the relationship must have the same number of columns". I'm doing this by in SQLSMS by going to the Keys 'folder' and adding a FK. Is there something that I am doing wrong here, I don't understand why the tables would have to have the same number of columns for me to add a FK relationship between the tables?

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• How to later assign value to optional attribute of NSManagedObject in a NSManagedObjectModel having

  - by Kundan

  I am using coredata framework. In my NSManagedObjectModel i am using three entities that are Class, Student and Score where class and student have one-to-many & inverse relationship and Student and Score have also inverse but one-one relationship. Score entity has all optional attributes and having default '0' decimalVaue, which is not assigned at the time new Student is added. But later i want to assign them score individually and also to particular attribute not all of score attributes in a go. I am able to create and add Students to particular Class but dont have any idea how to call particular student and assign them score. For example I want to assign Score'attribute "dribbling" [there are many attributes like "tackling"] a decimal value to Student "David" of Class "Soccer" ,how i can do that? Thanks in advance for any suggestion.

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• Rails has_and_belongs_to_many join across 3 tables

  - by Birdman

  I have a three models: listing, category, and site. There is a many to many relationship between listing and site and there is a many to many relationship between listing and category. A listing thus belongs to one or more sites and one or more categories (a listing can appear on multiple sites and multiple categories). Given a site id and a category id, I want a set of all the listings. I understand how to get the listings from a site id (listings = site.listings) and how to get the listings from a category id (listings = category.listings), but how do I get the triple join of the set of listings from both a site id and category id? The sql would look something like (sit_id and cat_id are input): select l.name from listings l, categories_listings cl, listings_sites, ls where cl.category_id = cat_id and ls.site_id = sit_id and cl.listing_id = l.id and ls.listing_id = l.id Thanks in advance

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• Fluent many-to-many: Deleting one end does not remove the entry in the relation table

  - by Kristoffer

  I have two classes (Parent, Child) that have a many-to-many relationship that only one end (Parent) knows about. My problem is that when I delete a "relation unaware" object (Child), the record in the many-to-many table is left. I want the relationship to be removed regardless of which end of it is deleted. How can I do that with Fluent NHibernate mappings, without adding a Parent property on Child? The classes: public class Parent { public Guid Id { get; set; } public IList<Child> Children { get; set; } } public class Child { public Guid Id { get; set; } // Don't want the property below: // public Parent Parent { get; set; } }

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• How to get null when use head funtion with a empty list in cypher?

  - by PeaceMaker

  I have a cypher query like this. START dep=node:cities(city_code = "JGS"), arr=node:cities(city_code = "XMN") MATCH dep-[way:BRANCH2BRANCH_AIRWAY*0..1]->()-->arr RETURN length(way), transfer.city_code, extract(w in way: w.min_consume_time) AS consumeTime The relationship named "way" is a optional one, so the property named "consumeTime" will be a empty list when the relationship "way" not exsit. The query result is: | 0 | "JGS" | [] | | 1 | "SZX" | [3600] | When I want to use the head function with the property "consumeTime", it return a error "Invalid query: head of empty list". How can I get a result like this? | 0 | "JGS" | null | | 1 | "SZX" | 3600 |

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• Denormalize for Simplicity: Ungood idea?

  - by yar

  After reading this question, I've learned that denormalization is not a solution for simplicity. What about this case? I have news-articles which have a list of sites-article-will-be-published-to. The latter can be expressed in normalized fashion either by table and a many-to-many relationship (via a cross-table, I think). But the simple solution is to just throw a bunch of booleans for the sites-article-will-be-published-to. Assuming the sites are: small in number will not change over time have no fields themselves, except a name Is this still a terrible idea? The many-to-many relationship seems somewhat cumbersome, but I've done it before in cases like this (and it seemed cumbersome). Note: I'm doing this in Rails, where it's not that painful.

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• What database table structure should I use for versions, codebases, deployables?

  - by Zac Thompson

  I'm having doubts about my table structure, and I wonder if there is a better approach. I've got a little database for version control repositories (e.g. SVN), the packages (e.g. Linux RPMs) built therefrom, and the versions (e.g. 1.2.3-4) thereof. A given repository might produce no packages, or several, but if there are more than one for a given repository then a particular version for that repository will indicate a single "tag" of the codebase. A particular version "string" might be used to tag a version of the source code in more than one repository, but there may be no relationship between "1.0" for two different repos. So if packages P and Q both come from repo R, then P 1.0 and Q 1.0 are both built from the 1.0 tag of repo R. But if package X comes from repo Y, then X 1.0 has no relationship to P 1.0. In my (simplified) model, I have the following tables (the x_id columns are auto-incrementing surrogate keys; you can pretend I'm using a different primary key if you wish, it's not really important): repository - repository_id - repository_name (unique) ... version - version_id - version_string (unique for a particular repository) - repository_id ... package - package_id - package_name (unique) - repository_id ... This makes it easy for me to see, for example, what are valid versions of a given package: I can join with the version table using the repository_id. However, suppose I would like to add some information to this database, e.g., to indicate which package versions have been approved for release. I certainly need a new table: package_version - version_id - package_id - package_version_released ... Again, the nature of the keys that I use are not really important to my problem, and you can imagine that the data column is "promotion_level" or something if that helps. My doubts arise when I realize that there's really a very close relationship between the version_id and the package_id in my new table ... they must share the same repository_id. Only a small subset of package/version combinations are valid. So I should have some kind of constraint on those columns, enforcing that ... ... I don't know, it just feels off, somehow. Like I'm including somehow more information than I really need? I don't know how to explain my hesitance here. I can't figure out which (if any) normal form I'm violating, but I also can't find an example of a schema with this sort of structure ... not being a DBA by profession I'm not sure where to look. So I'm asking: am I just being overly sensitive?

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• Django: Extending User Model - Inline User fields in UserProfile

  - by Jack Sparrow

  Is there a way to display User fields under a form that adds/edits a UserProfile model? I am extending default Django User model like this: class UserProfile(models.Model): user = models.OneToOneField(User, unique=True) about = models.TextField(blank=True) I know that it is possible to make a: class UserProfileInlineAdmin(admin.TabularInline): and then inline this in User ModelAdmin but I want to achieve the opposite effect, something like inverse inlining, displaying the fields of the model pointed by the OneToOne Relationship (User) in the page of the model defining the relationship (UserProfile). I don't care if it would be in the admin or in a custom view/template. I just need to know how to achieve this. I've been struggling with ModelForms and Formsets, I know the answer is somewhere there, but my little experience in Django doesn't allow me to come up with the solution yet. A little example would be really helpful!

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• Saving a Django form with a Many2Many field with through table

  - by PhilGo20

  So I have this model with multiple Many2Many relationship. 2 of those (EventCategorizing and EventLocation are through tables/intermediary models) class Event(models.Model): """ Event information for Way-finding and Navigator application""" categories = models.ManyToManyField('EventCategorizing', null=True, blank=True, help_text="categories associated with the location") #categories associated with the location images = models.ManyToManyField(KMSImageP, null=True, blank=True) #images related to the event creator = models.ForeignKey(User, verbose_name=_('creator'), related_name="%(class)s_created") locations = models.ManyToManyField('EventLocation', null=True, blank=True) In my view, I first need to save the creator as the request user, so I use the commit=False parameter to get the form values. if event_form.is_valid(): event = event_form.save(commit=False) #we save the request user as the creator event.creator = request.user event.save() event = event_form.save_m2m() event.save() I get the following error: *** TypeError: 'EventCategorizing' instance expected I can manually add the M2M relationship to my "event" instance, but I am sure there is a simpler way. Am I missing on something ?

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• Rails: Design Pattern to Store Order of Relations

  - by ChrisInCambo

  Hi, I have four models: Customer, QueueRed, QueueBlue, QueueGreen. The Queue models have a one to many relationship with customers A customer must always be in a queue A customer can only be in one queue at a time A customer can change queues We must be able to find out the customers current position in their respective queue In an object model the queues would just have an array property containing customers, but ActiveRecord doesn't have arrays. In a DB I would probably create some extra tables just to handle the order of the stories in the queue. My question is what it the best way to model the relationship in ActiveRecord? Obviously there are many ways this could be done, but what is the best or the most in line with how ActiveRecord should be used? Cheers, Chris

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• Django: Set foreign key using integer?

  - by User

  Is there a way to set foreign key relationship using the integer id of a model? This would be for optimization purposes. For example, suppose I have an Employee model: class Employee(models.Model): first_name = models.CharField(max_length=100) last_name = models.CharField(max_length=100) type = models.ForeignKey('EmployeeType') and EmployeeType(models.Model): type = models.CharField(max_length=100) I want the flexibility of having unlimited employee types, but in the deployed application there will likely be only a single type so I'm wondering if there is a way to hardcode the id and set the relationship this way. This way I can avoid a db call to get the EmployeeType object first.

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• Foreign key on table A --> B, AND foreign key on table B --> A. How is this done?

  - by unclaimedbaggage

  Hi, I have two tables - 'business' and 'business_contacts'. The business_contact table has a many-to-one relationship with the business table. Furthermore, each business has a 'primary contact' field - which I'd assume is a one-to-many relationship with the business_contacts table. The problem, of course, is that this creates a catch-22 for data insertion. Since neither field can be null, I can't insert a business_contact until I have a corresponding business, but I can't insert a business until I have a corresponding business_contact. If anyone could help me get my head around how mutual one-to-many relationships are supposed to be dealt with I'd be most appreciative. (Project being done in MySQL if it makes any difference)

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