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• AND NSPedicate on Core Data relationships

  - by jesse001

  I'm having trouble compounding NSPredicate with AND, although using OR works fine. Imagine 2 entities, Doctor and Patient. Doctors can have many patients and patients many doctors. I want to find doctors that, say, have both person1 and person2 as patients. I expected this to work but it returns none. NSPredicate *predicate = [NSPredicate predicateWithFormat:@"ANY patients matches 'person1&&person2'"]; If I change && to ||, I get all doctors that have person1 or person2 as I'd expect. Thanks in advance for your help.

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• Retrieving Relationships from within two arrays of pointers

  - by DanF

  In a portion of a program I'm working on, I need to count all the times each person has worked on projects with each other person. Let's say we have "Employee" entities and "Session" entities. In each session, there are four project types, "A", "B", "C", & "D", each a many-to-many relationship to Employees. I'm making a loop to systematically review every person a selected person has worked with. First, I put all their project types in a single array, so it's easier to loop through, but by the time I ask the last nested Project for its Employee members, I get an "unrecognized selector" error. IBOutlet NSArrayController * list; int x; for(x = 0; x < [list count]; x++){ NSArray *A = [[list objectAtIndex:x] valueForKey:@"projectAs"]; NSArray *A = [[list objectAtIndex:x] valueForKey:@"projectBs"]; NSArray *A = [[list objectAtIndex:x] valueForKey:@"projectCs"]; NSArray *A = [[list objectAtIndex:x] valueForKey:@"projectDs"]; NSArray *masterList = [[NSArray alloc] initWithObjects: projectAs, projectBs, projectCs, projectDs, nil]; int y; for(y = 0; y < [masterList count]; y++){ int z; for(z = 0; z < [[masterlist objectAtIndex:y] count]; z++){ //And now to make an Array of this employee's partners on the selected object, to run comparisons on. //I also have an array of keys for each session's teams, so that's what I'm referencing here: NSArray * thisTeam = [list objectAtIndex:y] objectAtIndex:z] valueForKey:projectKey]; This throws an exception... namely, -[_NSFaultingMutableSet objectAtIndex:]: unrecognized selector sent to instance What's wrong with that last Array creation?

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• Hibernate subclass with foreign key relationships

  - by shikarishambu

  I need some help defining the following object hierarchy/ database relationship in Hibernate From the object sense – Agent is inherited from Person and Agency is inherited from Organization. they are inherited from Party which can have multiple Addresses associated with it The database consists of Agent - ID - Name -PartyID (references Party.ID) Agency -ID -Name -PartyID (references Party.ID) Address -AddrID -PartyID (references Party.ID) -Street Party. -PartyID

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• Foreign Key Relationships

  - by Yehonathan Quartey

  I have two models class Subject(models.Model): name = models.CharField(max_length=100,choices=COURSE_CHOICES) created = models.DateTimeField('created', auto_now_add=True) modified = models.DateTimeField('modified', auto_now=True) syllabus = models.FileField(upload_to='syllabus') def __unicode__(self): return self.name and class Pastquestion(models.Model): subject=models.ForeignKey(Subject) year =models.PositiveIntegerField() questions = models.FileField(upload_to='pastquestions') def __unicode__(self): return str(self.year) Each Subject can have one or more past questions but a past question can have only one subject. I want to get a subject, and get its related past questions of a particular year. I was thinking of fetching a subject and getting its related past question. Currently am implementing my code such that I rather get the past question whose subject and year correspond to any specified subject like this_subject=Subject.objects.get(name=the_subject) thepastQ=Pastquestion.objects.get(year=2000,subject=this_subject) I was thinking there is a better way to do this. Or is this already a better way? Please Do tell ?

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• SQL query help - finding rows with no relationships

  - by DD

  Consider a DB with a Client table and a Book table: Client: person_id Book: book_id Client_Books: person_id,book_id How would you find all the Person ids which have no books? (without doing an outer join and looking for nulls)

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• Traversing ORM relationships returns duplicate results

  - by NKing253

  I have 4 tables -- store, catalog_galleries, catalog_images, and catalog_financials. When I traverse the relationship from store --> catalog_galleries --> catalog_images in other words: store.getCatalogGallery().getCatalogImages() I get duplicate records. Does anyone know what could be the cause of this? Any suggestions on where to look? The store table has a OneToOne relationship with catalog_galleries which in turn has a OneToMany relationship with catalog_images and an eager fetch type. The store table also has a OneToMany relationship with catalog_financials.

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• Is there a way to put relationships/contraints into CSS?

  - by hekevintran

  In every design tool or art principle I've heard of, relationships are a central theme. By relationships I mean the thing you can do in Adobe Illustrator to specify that the height of one shape is equal to half the height of another. You cannot express this information in CSS. CSS hard-codes all values. Using a language like LESS that allows variables and arithmetic you can get closer to relationships but it's still a CSS variant. This inability in my mind is the biggest problem with CSS. CSS is supposed to be a language that describes the visual component of a Web page but it ignores relationships and contraints, ideas that are at the core of art. How possible is it to imagine a new Web design language that can express relationships and contraints that can be implemented in JavaScript using the current CSS properties?

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• Many-to-Many Relationship (with properties) in Google App Engine for Java

  - by rvandervort

  I understand from the official documentation on unowned relationships that the app must use sets of Key objects on either side of the relationship. This makes perfect sense. Coming from many years of RDBM-style programming, though, I'm pretty confused about how I can model properties of that relationship itself. For example, if I have entities Category and Entry in my many-to-many relationship and would like to persist a dateAdded property, or some other data that are only relevant when both sides of the relationship are known. I suppose it would be possible to create a third class : CategoryEntry that links the two, but this seems like a kludge. What is the proposed way to model this kind of situation ?

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• [Rails3] How to do multiple many to many relationships between the same two tables.

  - by Kurt

  Hi. I have a model of a club where I want to model the two entities Meeting and Member. There are actually two many-to-many relationships between these entities though, as for any meeting a Member can either be a Speaker or a Guest. Now I am an OO thinker, so would normally just create the two classes and each one would just have two arrays of the other inside, but rails is making me think a bit more data centric here, so I realise I need to break these M2M relationships up with join tables Speakers and Guests which I have done, but now I am having trouble describing the relationships in the models. The two join table models both have "belongs_to :meeting" and "belongs_to :member" and I think that should be sufficient. I am not however sure about the Meeting and Member models though. Each one has "has_many :guests" and "has_many: speakers" but I am not sure if I also want to go: has_many :members, :through = :guests has_many :members, :through = :speakers But I suspect that this is like declaring two "members" that will clash. I also thought about: has_many :guests, :through = :guests has_many :speakers, :through = :speakers Does that make sense? How would ActiveRecord know that they are in fact Members? I have found heaps of examples of polymorphic m2m relationships and m2m relationships where 1 table references itself, but no good examples to help me mode this situation where two separate tables have two different m2m relationships. Anyone got any tips?

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• Circular reference error when outputting LINQ to SQL entities with relationships as JSON in an ASP.N

  - by roosteronacid

  Here's a design-view screenshot of my dbml-file. The relationships are auto-generated by foreign keys on the tables. When I try to serialize a query-result into JSON I get a circular reference error..: public ActionResult Index() { return Json(new DataContext().Ingredients.Select(i => i)); } But if I create my own collection of "bare" Ingredient objects, everything works fine..: public ActionResult Index() { return Json(new Entities.Ingredient[] { new Entities.Ingredient(), new Entities.Ingredient(), new Entities.Ingredient() }); } ... Also; serialization works fine if I remove the relationships on my tables. How can I serialize objects with relationships, without having to turn to a 3rd-party library? I am perfectly fine with just serializing the "top-level" objects of a given collection.. That is; without the relationships being serialized as well.

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• Core Data migration of to-one relationship to to-many relationship

  - by westsider

  I have a deployed app that samples measurements from sensors (e.g., Temp °C, Pressure kPa). The user can create Experiments and collect samples. Each sample is stored as a Run, such that there is a one-to-many relationship from Experiment to Run. In the interest of performance, Run has a to-one relationship with Data entity (which is where the actual raw data is stored); this allows some Run attributes to be loaded without necessarily loading lots of data. Most of our sensors have multiple measurements, so it would be nice to store all the data that is actually being sampled. But this means that the Run <--- Data relationship needs to become Run <-- Data (to use Xcode's convention). I am faced with trying to migrate data from old Run to-one Data model to new Run to-many Data model. Can this be done using Mapping Models? If so, does anyone have any pointers to examples? If not, does anyone have any pointers to examples of how to do that? Thanks for any pointers or advice.

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• Django generic relation field reports that all() is getting unexpected keyword argument when no args

  - by Joshua

  I have a model which can be attached to to other models. class Attachable(models.Model): content_type = models.ForeignKey(ContentType) object_pk = models.TextField() content_object = generic.GenericForeignKey(ct_field="content_type", fk_field="object_pk") class Meta: abstract = True class Flag(Attachable): user = models.ForeignKey(User) flag = models.SlugField() timestamp = models.DateTimeField() I'm creating a generic relationship to this model in another model. flags = generic.GenericRelation(Flag) I try to get objects from this generic relation like so: self.flags.all() This results in the following exception: >>> obj.flags.all() Traceback (most recent call last): File "<console>", line 1, in <module> File "/usr/local/lib/python2.6/dist-packages/django/db/models/manager.py", line 105, in all return self.get_query_set() File "/usr/local/lib/python2.6/dist-packages/django/contrib/contenttypes/generic.py", line 252, in get_query_set return superclass.get_query_set(self).filter(**query) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 498, in filter return self._filter_or_exclude(False, *args, **kwargs) File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py", line 516, in _filter_or_exclude clone.query.add_q(Q(*args, **kwargs)) File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py", line 1675, in add_q can_reuse=used_aliases) File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py", line 1569, in add_filter negate=negate, process_extras=process_extras) File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py", line 1737, in setup_joins "Choices are: %s" % (name, ", ".join(names))) FieldError: Cannot resolve keyword 'object_id' into field. Choices are: content_type, flag, id, nestablecomment, object_pk, timestamp, user >>> obj.flags.all(object_pk=obj.pk) Traceback (most recent call last): File "<console>", line 1, in <module> TypeError: all() got an unexpected keyword argument 'object_pk' What have I done wrong?

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• JPA - Entity design problem

  - by Yatendra Goel

  I am developing a Java Desktop Application and using JPA for persistence. I have a problem mentioned below: I have two entities: Country City Country has the following attribute: CountryName (PK) City has the following attribute: CityName Now as there can be two cities with same name in two different countries, the primaryKey for City table in the datbase is a composite primary key composed of CityName and CountryName. Now my question is How to implement the primary key of the City as an Entity in Java @Entity public class Country implements Serializable { private String countryName; @Id public String getCountryName() { return this.countryName; } } @Entity public class City implements Serializable { private CityPK cityPK; private Country country; @EmbeddedId public CityPK getCityPK() { return this.cityPK; } } @Embeddable public class CityPK implements Serializable { public String cityName; public String countryName; } Now as we know that the relationship from Country to City is OneToMany and to show this relationship in the above code, I have added a country variable in City class. But then we have duplicate data(countryName) stored in two places in the City class: one in the country object and other in the cityPK object. But on the other hand, both are necessary: countryName in cityPK object is necessary because we implement composite primary keys in this way. countryName in country object is necessary because it is the standard way of showing relashionship between objects. How to get around this problem?

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• PHP Doctrine - YAML syntax help. Default value for many to many relationship?

  - by Dan

  Hi, I have the following YAML schema for organising users in Doctrine: Person: tableName: people columns: id: type: integer primary: true autoincrement: true firstname: type: string notnull: true lastname: type: string notnull: true User: inheritance: extends: Person type: column_aggregation keyField: type keyValue: 1 Userdetails: columns: person_id: type: integer primary: true password: type: string notnull: true relations: User: foreignType: one local: person_id onDelete: CASCADE onUpdate: CASCADE Group: tableName: groups columns: id: type: integer primary: true autoincrement: true name: type: string notnull: true UserGroup: columns: group_id: type: integer primary: true person_id: type: integer primary: true relations: User: foreignType: many local: person_id Group: foreignType: many Basically, any people who are users will belong to one or more groups. Is there any way to add new users to a particular group by default? Any advice appreciated. Thanks

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• Checking for reciprocal relationships in mysql. A trivial one table problem.

  - by calumbrodie

  I have a mysql table that stores relationships. Items can be related to another item in one direction, or both items can be related to each other. I want to return all items related to my primary item - but I also want to check to see if the related item has a 'reverse relationship' to the current item and show this as a boolean |--------------|---------------| | SKU | related_SKU | |--------------|---------------| | 0001 | 0099 | | 0002 | 0099 | | 0099 | 0001 | |--------------|---------------| If I want to get all relationships for SKU=0001 SELECT related_SKU from relationships where SKU='0001' returns |--------------| | related_SKU | |--------------| | 0099 | |--------------| but what I want is |--------------|---------------| | related_SKU | reciprocal | |--------------|---------------| | 0099 | 1 | |--------------|---------------| or SELECT related_SKU from relationships where SKU='0002' |--------------|---------------| | related_SKU | reciprocal | |--------------|---------------| | 0099 | 0 | |--------------|---------------| What's the best way to do this?

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• Having to insert a record, then update the same record warrants 1:1 relationship design?

  - by dianovich

  Let's say an Order has many Line items and we're storing the total cost of an order (based on the sum of prices on order lines) in the orders table. -------------- orders -------------- id ref total_cost -------------- -------------- lines -------------- id order_id price -------------- In a simple application, the order and line are created during the same step of the checkout process. So this means INSERT INTO orders .... -- Get ID of inserted order record INSERT into lines VALUES(null, order_id, ...), ... where we get the order ID after creating the order record. The problem I'm having is trying to figure out the best way to store the total cost of an order. I don't want to have to create an order create lines on an order calculate cost on order based on lines then update record created in 1. in orders table This would mean a nullable total_cost field on orders for starters... My solution thus far is to have an order_totals table with a 1:1 relationship to the orders table. But I think it's redundant. Ideally, since everything required to calculate total costs (lines on an order) is in the database, I would work out the value every time I need it, but this is very expensive. What are your thoughts?

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• Entity Framework 4 Hiding Underlying Resolver Tables when model is generated from database

  - by grrrrrrrrrrrrr

  When creating an entity framework model from scratch it is possible to specify a Many to Many relationship in the model. e.g Entity1 * ----- * Entity2 When a database is then generated from this, a resolver table is then created automatically between the two entities, this is hidden in the code model, allowing direct access to each of the entities via properties. e.g. Entity1 ----* ResolverEntity *----- Entity2 My question is, when a model is generated from an existing database, which contains resolver tables, is it possible to create the same effect so the resolver tables do not appear in the generated object model? When I have attempted this, the entity framework appears to create entities in the model for the resolver tables with no obvious way of hiding them in the object model. Thanks.

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• InnoDB - Two foreign keys on the same column from one table

  - by makeflo

  Hey Guys, i have a project table which has a image_id field and a newsimage_id field. Both are linked to the image table. But InnoDB doesn't allow me to set a foreign key for both fields to the same column (id). Is there a way I can do this or is it not possible? I'm using MySQL through MAMP. Thanks in advance!!

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• What are other ideologies to establish relationships between distinct users besides followers/following and friends?

  - by user784637

  Websites like myspace and facebook establish relationships between distinct users using the "friending" ideology, where one user sends a request to be accepted by another user in order for them to have the mutual permission to do stuff like post messages on each others walls. Less restrictive than the "friending" ideology, Twitter and instagram use the followers/following ideology where you can subscribe to the tweets or posts of another user without their permission. Less restrictive than the "followers/following" ideology, email and calling someone on the phone allows you to directly contact anyone. Are there other ideologies that have been successfully implemented either in social networking sites or other real world constructs to establish relations between users?

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• How do I express subtle relationships in my data?

  - by Chuck H

  "A" is related to "B" and "C". How do I show that "B" and "C" might, by this context, be related as well? Example: Here are a few headlines about a recent Broadway play: 1 - David Mamet's Glengarry Glen Ross, Starring Al Pacino, Opens on Broadway 2 - Al Pacino in 'Glengarry Glen Ross': What did the critics think? 3 - Al Pacino earns lackluster reviews for Broadway turn 4 - Theater Review: Glengarry Glen Ross Is Selling Its Stars Hard 5 - Glengarry Glen Ross; Hey, Who Killed the Klieg Lights? Problem: Running a fuzzy-string match over these records will establish some relationships, but not others, even though a human reader could pick them out from context in much larger datasets. How do I find the relationship that suggests #3 is related to #4? Both of them can be easily connected to #1, but not to each other. Is there a (Googlable) name for this kind of data or structure? What kind of algorithm am I looking for? Goal: Given 1,000 headlines, a system that automatically suggests that these 5 items are all probably about the same thing. To be honest, it's been so long since I've programmed I'm at a loss how to properly articulate this problem. (I don't know what I don't know, if that makes sense). This is a personal project and I'm writing it in Python. Thanks in advance for any help, advice, and pointers!

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• I need a form to tie MySQL Records together (i.e., many-to-many relationships).

  - by John R

  I need a HTML-based form to tie database records together. The user scenario that I envision is somthing like this: A super-user does a search of the database and is delivered a table of records based on that search; each record is numbered with the database-record id. There would also be two text fields next to each record. These text fields would allow: the user to make a reference from one record to another. For example, a user could enter into record id #457 that there is a correlation with record ID #242. The user would also describe the type of relationship it is. This could be with a simple integer that represents the type of relationship between the two records. When the super-user hits the submit button, all of these relationships are saved in a mySqljoin table. One option is to give me advice on how to implement and code this myself in PHP. However, before I reinvent the wheel, another option is to lead me to a free script that does something similar.

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• How Many HABTM relationships in cakephp is too many?

  - by user559540

  Hi all, I'm struggling with deciding how many HABTM relationships I really need in my cakephp app. I guess I don't quite get what "has" truly means. I don't want to have more HABTM tables than necessary. Here's what I have in my database: Users Properties Leases Payments Repairs user HABTM properties, user HABTM leases, user HABTM users, user HABTM repairs, property hasMany repairs, property hasMany leases, lease hasMany repairs. Also, I have two aliases for my users model (manager and tenant). This is one of the reasons I ended up with so many HABTM relationships, but I'm not sure it's necessary. Do I have too many user HABTM relationships? Would it be better to just have cake recurse through my models? Thanks!

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• T-SQL Script to Delete All The Relationships Between A Bunch Of Tables in a Schema and Other Bunch i

  - by Galilyou

  Guys, I have a set of tables (say Account, Customer) in a schema (say dbo) and I have some other tables (say Order, OrderItem) in another schema (say inventory). There's a relationship between the Order table and the Customer table. I want to delete all the relationships between the tables in the first schema (dbo) and the tables in the second schema (inventory), without deleting the relationships between tables inside the same schema. Is that possible? Any help appreciated.

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• "Too many indexes on table" error when creating relationships in Microsoft Access 2010.

  - by avianattackarmada

  I have tblUsers which has a primary key of UserID. UserID is used as a foreign key in many tables. Within a table, it is used as a foreign key for multiple fields (e.g. ObserverID, RecorderID, CheckerID). I have successfully added relationships (with in the the MS Access 'Relationship' view), where I have table aliases to do the multiple relationships per table: *tblUser.UserID - 1 to many - tblResight.ObserverID *tblUser_1.UserID - 1 to many - tblResight.CheckerID After creating about 25 relationships with enforcement of referential integrity, when I try to add an additional one, I get the following error: "The operation failed. There are too many indexes on table 'tblUsers.' Delete some of the indexes on the table and try the operation again." I ran the code I found here and it returned that I have 6 indexes on tblUsers. I know there is a limit of 32 indexes per table. Am I using the relationship GUI wrong? Does access create an index for the enforcement of referential integrity any time I create a relationship (especially indexes that wouldn't turn up when I ran the script)? I'm kind of baffled, any help would be appreciated.

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• Does Python Django support custom SQL and denormalized databases with no Foreign Key relationships?

  - by Jay

  I've just started learning Python Django and have a lot of experience building high traffic websites using PHP and MySQL. What worries me so far is Python's overly optimistic approach that you will never need to write custom SQL and that it automatically creates all these Foreign Key relationships in your database. The one thing I've learned in the last few years of building Chess.com is that its impossible to NOT write custom SQL when you're dealing with something like MySQL that frequently needs to be told what indexes it should use (or avoid), and that Foreign Keys are a death sentence. Percona's strongest recommendation was for us to remove all FKs for optimal performance. Is there a way in Django to do this in the models file? create relationships without creating actual DB FKs? Or is there a way to start at the database level, design/create my database, and then have Django reverse engineer the models file?

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