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• Active Record/ORM vs Normal Forms?

  - by Arsenal

  Hello, I've been playing around with Active Record a bit, and I have noticed that A.C./ORM always uses the following database model when creating a one-to-one relationship Person id | country_id | name | ... Country id | tld | name | ... No I wondered, isn't this a violiation of the third Normal Form? This clearly states "Every non-prime attribute is non-transitively dependent on every key of the table". Well this country_id isn't dependent of personid is it? So is this wrong or am I just not getting the point?

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• Core Data table record count

  - by user339633

  I have an entity called Person and it has a relationship called participatingGames, to another entity called GameParticipant. I (apparently) can retrieve the number of matches in the GameParticipant entity using this simple code in the Person object I created from the entity in the model: [self.participatingGames count]; However, I'd just like to retrieve the number of Person records and one might guess the syntax for this is just as simple. I have lots of books including those by Jeff LaMarche, but those sources and what I find around here make me wonder if I need to set up a fetchedResultsController just to know the count of some entity. My background is in SQL, so of course it seems odd that what would take 15 seconds to code in any other environment seems like such a well-guarded secret in Core Data. I'm using iPhone SDK 3.1.4 under OSX 10.5.8 Suggestions?

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• Get group key from bridge table

  - by Mads Jensen

  I'm developing an ETL process, and need a bridge table for a one-to-many relationship between a fact table and a dimension table (MySQL database). There is a limited number of combinations (some thousands), so I want to re-use group keys from the bridge table to to limit the size. Any group of dimensions belonging to a fact row will consist of a number of dimension keys (1 to around 15), assigned to a unique group key, as below: group_key | dimension_key ----------------------- 1 | 1 1 | 3 1 | 4 2 | 1 2 | 2 2 | 3 3 | 1 3 | 4 How do I go about retrieving the unique group key for the dimensions 1,3,4 (ie. 1).

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• iPhone Development - Using NSPredicate to retrieve most recently added record from CoreData

  - by Mustafa

  I want to retrieve the most recently added record from CoreData. I was wondering if that's possible using NSPredicate? If so, how? e.g. i have a one-to-many relationship between Department and Staff, and i want to fetch the Staff record that was most recently employed. The Staff table has a date field which can be used. I don't want to fetch all the Staff records and then look for the right one. Note that CoreData stores the related records in an NSSet.

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• predicate subquery to return items by matching tags

  - by user3411663

  I have a many-to-many relationship between two entities; Item and Tag. I'm trying to create a predicate to take the selectedItem and return a ranking of items based on how many similar tags they have. So far I've tried: NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SUBQUERY(itemToTag, $item, $item in %@).@count > 0", selectedItem.itemToTag]; Any other iterations that have failed. It currently only returns the selectedItem in the list. I've found little on Subquery. Is there a guru out there that can help me refine this? Thanks in advance for the help!

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• Django: Overriding ModelAdmin save_model not working

  - by tufelkinder

  Even after obj.save(), the obj still does not have an id, so I cannot access or manipulate the m2m records. Just keep getting a "instance needs to have a primary key value before a many-to-many relationship can be used" error. def save_model(self, request, obj, form, change): obj.save() # this doesn't work super(Table2Admin, self).save_model(request, obj, form, change) # still doesn't save for tb1 in obj.table1.all: tb1_obj = ThroughTable.objects.get(table1=bk, table2=obj) # do other stuff What am I doing wrong? Why do I need to do to save this model?

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• Dealing w/ Sqlite Join results in a cursor

  - by Bill

  I have a one-many relationship in my local Sqlite db. Pretty basic stuff. When I do my left outer join I get back results that look like this: the resulting cursor has multiple rows that look like this: A1.id | A1.column1 | A1.column2 | B1.a_id_fk | B1.column1 | B1.column2 A1.id | A1.column1 | A1.column2 | B2.a_id_fk | B2.column1 | B2.column2 and so on... Is there a standard practice or method of dealing with results like this ? Clearly there is only A1, but it has many B-n relationships. I am coming close to using multiple queries instead of the "relational db way". Hopefully I am just not aware of the better way to do things. I intend to expose this query via a content provider and I would hate for all of the consumers to have to write the same aggregation logic.

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• Recursive query question - break rows into columns?

  - by Stew

  I have a table "Families", like so FamilyID PersonID Relationship ----------------------------------------------- F001 P001 Son F001 P002 Daughter F001 P003 Father F001 P004 Mother F002 P005 Daughter F002 P006 Mother F003 P007 Son F003 P008 Mother and I need output like FamilyID PersonID Father Mother ------------------------------------------------- F001 P001 P003 P004 F001 P002 P003 P004 F001 P003 F001 P004 F002 P005 P006 F002 P006 F003 P007 P008 F003 P008 In which the PersonID of the Father and Mother for a given PersonID are listed (if applicable) in separate columns. I know this must be a relatively trivial query to write (and therefore to find instructions for), but I can't seem to come up with the right search terms. Searching "SQL recursive queries" has gotten me closest, but I can't quite translate those methods to what I'm trying to do here. I'm trying to learn, so multiple methods are welcome, as is vocabulary I should read up on. Thanks!

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• java tool for debugging

  - by user269723

  Hi experts, Currently we are studying the java based tool which is primararily Reporting tool.It was developed in 2000/2001 period and uses many open source libraries like Apache Avalon/Mx4J.Adaptor/edu.Oswego(java concurrent package) etc. Tool uses jdk 1.3.1 and goal is to upgrade to jdk 1.5.We have also been asked to remove these 'outdated' packages and replace by standard java packages if possible. Unfortunately we have the code available for study but lacks any documentation and really difficult to track the flow(Total number of classes written might be more than 1000) during debugging. Whats the best way to understand this kind of tool? any Graphical tool to see the relationship between the classes? Thanks SR

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• Database layout tagging system

  - by Kurresmack

  I am creating a web site for a customer and they want to be able to create articles. My idea is to tag them so I am going to implement the system. What is the best design, both from an architectural and a perfomance perspective: 1. To have table with all tags and then have a one to many relationship table that links a tag like this: articles table with ID tags table with ID one to many table with columns Article.ID and Tags.ID 2. To have one table with articles and one with tags for articles like this: articles table with ID tags table with Article.ID and tag text Thanks in advance!

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• Many to Many DataSet Insert to Database using Stored Procedures

  - by Jonn

  I'm trying to do a many-to-many bulk insert to the database using a list of three different types of models. The only tools I can use are stored procedures and datasets. (But I can't use DataSet fills or DataAdapters, just plain ol' Stored Procedures). Is there an easy way to pass multiple values, let alone, pass three different lists and bulk insert them to a table in the database using stored procedures? (As specified in the title, the three tables are actually two tables and a third table to establish the many-to-many relationship between the two.)

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• Eager fetching of children with JDO (Datanucleus)

  - by Jan

  Hi, can JDO fetch all children of a database model at once? Like: class Parent { @Persistent(mappedBy="parent") private Set<Children> children; } class Children { @Persistent private Parent parent; @Persistent private String name; } In my case, I have a large number of Parents which I fetch at once. Accessing their children then takes a lot of time because they are fetched lazily. Does JDO (Datanucleus) support their fetching at once, togehter with the Parents? I also tried to fetch all Children independantly with another quey and put them into the Level2 cache afterwards, but still they are fetched (maybe jdo doesn't know about their relationship? Because the ForeignKey (parent-id) hasn't been fetched at first?) Any ideas how to read the data structure faster? Cheers, Jan

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• Ruby on Rails: How to find all items with a hash that contain a specific value...

  - by kingjeffrey

  Suppose I have three models: Student, SchoolClass, and DayOfWeek. There is a HABTM relationship between Student and SchoolClass, and between SchoolClass and DayOfWeek. What I'd like to do is find all school classes belonging to a given student that meet on Monday. Now I suppose I could do something like: @student = Student.find(:student_id) @student_classes = @student.school_classes.find(:all) @student_classes_on_monday = Array.new @student_classes.each do |student_class| if student_class.day_of_week.include?("Monday") @student_classes_on_monday << student_class end end But there has to be a more elegant way. Can you help me find it?

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• Cakephp, Retreive Data for HABTM Models using find

  - by user298079

  I am new to cakephp and I'm trying to accomplish something that should be relatively easy. I have 2 models projects & categories bind by HABTM relationship. I am trying to perform the following query - find all projects that belong to a category $projects = $this->Project->find('all', array('conditions' => array('Category.slug' => $category))); However when I'm doing so it generates an SQL error: SQL Error: 1054: Unknown column 'Category.slug' in 'where clause' What am I doing wrong??

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• How to explain to a client that you've gone over-budget and you'll need more money/time to deliver w

  - by General Tapioca

  My situation is that I have agreed on a per-project proposal with the client. The proposal is vague, but still names functionality in a way that can be argued as to whether it's included or not, while leaving some room for interpretation. I originally pressed as much as I could to get a per-month contract, arguing that the project is mostly non-predictable, but the client refused. Being a small company, I had to fold and signed a contract on an estimate based on my group's estimations. At this point we have reached completion on about 85% of the features (we think) but we ran out of budget. We have been working for almost two years with this client in previous contracts, and we have delivered a good product that they are happy with, so we have a good standing relationship. More info: -There has been a bit of scope-creep, but I don't think enough for me to hide behind that argument -We've been delivering partial releases about monthly. -We don't have systematic user-testing in place.

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• Partial form with nested routes

  - by jerhinesmith

  I have two models -- User and Entry -- that are related through a has_many relationship (a User has many Entries). I'm using RESTful routing, and have the following in my routes.rb file: map.resource :user, :controller => "users" do |user| user.resources :entries end This seems to work, but in my partial _form file, when I do this: form_for [@current_user, @entry] do |f| # Form stuff end It generates a URL like this: /user/entries.%23%3Cuser:0xb6a6aea8%3E instead of /user/entries Am I missing something? I should note that the correct classes are applied to the form when doing creation vs. editing, so it does seem to be correctly interpreting what I'm trying to do -- it's just that I can't submit the form to an invalid url.

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• SQL join to grab data from same table via intermediate table

  - by Sergio

  Hi Could someone help me with building the following query. I have a table called Sites, and one called Site_H. The two are joined by a foreign key relationship on page_id. So the Sites table contains pages, and the Site_H table shows which pages any given page is a child of by having another foreign key relation back to the site table with a column called ParentOf. So, a page can be have another page as a parent. Other data is stored in the Site_H table such as position etc, hence why it is separated out. I would like a query that returns the details of a page along with the details of its parent page. I just cant quite think about how to structure the SQL. Thanks

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• Star schema [fact 1:n dimension]...how?

  - by Mike Gates

  I am a newcomer to data warehouses and have what I hope is an easy question about building a star schema: If I have a fact table where a fact record naturally has a one-to-many relationship with a single dimension, how can a star schema be modeled to support this? For example: Fact Table: Point of Sale entry (the measurement is DollarAmount) Dimension Table: Promotions (these are sales promotions in effect when a sale was made) The situation is that I want a single Point Of Sale entry to be associated with multiple different Promotions. These Promotions cannot be their own dimensions as there are many many many promotions. How do I do this?

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• sql server 2005 - return single row when 2 records in right table

  - by Peanut

  Hi, I have two related sql server tables ... TableA and TableB. ***TableA - Columns*** TableA_ID INT VALUE VARCHAR(100) ***TableB - Columns*** TableB_ID INT TableA_ID INT VALUE VARCHAR(100) For every single record in TableA there are always 2 records in TableB. Therefore TableA has a one-to-many relationship with TableB. How could I write a single sql statement to join these tables and return a single row for each row in TableA that includes: a column for the VALUE column in the first related row in table B a column for the VALUE column in the second related row in table B? Thanks.

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• to-many Core Data fetch request behaves oddly with a new store

  - by Giao

  I have two entities, Department and Person. Department has a to-many relationship to Person. The Person entity has a hireDate property. I'm using the predicate "count(person) = 0 OR none person.hireDate %@" to find Departments without any Persons in them or Departments that haven't hired anyone since a recent date. When the app first starts up (new user experience) and Departments are inserted and no Person have been inserted, the fetch request with this predicate returns nothing. However, if I create insert a new Person entity and delete it, then save the store, the fetch request will return all the Departments. I've found a work around where, I just insert a new Person and delete it, then save the store, the fetch request as I expected it to work. I've found that inserting a new Person and deleting it without saving will not correct the problem. Is this a bug with Core Data or is this a bug with how I've designed my app?

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• Using a RegEx in a SQL Query

  - by Jim B

  Hey Everyone, Here's the situation I'm in: We have a field in our database that contains a 3 digit number, surrounded by some text. This number is actually a PK in another table, and I need to extract this out so I can implement a proper FK relationship. Here's an example of what would currently reside in the column: Some Text Goes Here - (305) Followed By Some More Text So, what I'm looking to do is extract the '305' from the column, and hopefully end up with a result that looks something like this (pseudo code) SELECT <My Extracted Value>, Original Column Text, Id FROM dbo.MyTable It seems to me that using a Regex match in my query is the most effective way to do this. Can anybody point me in the right direction?

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• Objective-C Custom extend

  - by ryanjm.mp

  I have a couple classes that have nearly identical code. Only a string or two is different between them. What I would like to do is to make them from another class that defines those functions and then uses constants or something else to define those strings that are different. I'm not sure if "___" is inheritance or extending or what. That is what I need help with. For example: objectA.m: -(void)helloWorld { NSLog("Hello %@",child.name); } objectBob.m: #define name @"Bob" objectJoe.m #define name @"Joe" (I'm not sure if it's legal to define strings, but this gets the point across) It would be ideal if objectBob.m and objectJoe.m didn't have to even define the methods, just their relationship to objectA.m. Is there any way to do something like this? If all else fails I'll just make objectA.m: -(void)helloWorld:(NSString *name) { NSLog("Hello %@",name); } And have the other files call that function (and just #import objectA.m).

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• Creating Two Cascading Foreign Keys Against Same Target Table/Col

  - by alram

  I have the following tables: user (userid int [pk], name varchar(50)) action (actionid int [pk], description nvarchar(50)) being referenced by another table that captures the relationship: <user1> <action>'s <user2>. I did this with the following table: userAction (userActionId int [pk], actionid int [fk: action.actionid], **userId1 int [fk ref's user.userid; on del/update cascade], userId2 int [fk ref's user.userid; on del/update cascade]**). However, when I try to save the userAction table i get an error because I have two cascading fk's against user.userid. Is there any way to remedy this or must I use a trigger?

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• Using STI path with same controller

  - by TenJack

  I am using STI and am wondering, do I have to have a separate controller for each model? I have a situation where I only use the create and edit actions for one model in the STI relationship, but I get an 'undefined method' error if I try to do a form for. More specifically, I have two models that inherit from List: class RegularList < List class OtherList < List and I have a lists controller that handles these actions, but I only create new models with RegularList using forms. i.e. the only situation where I use a form_for to create a new List object is with RegularList. What I would like to do is something like: class ListsController < ApplicationController def new @list = RegularList.new end otherwise the route for creating a new list looks like regular_list/new but I would like it to just be list/new. Thoughts?

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• Django show manytomanyfield on form when definition is on other model

  - by John

  Hi I have the definition for my manytomany relationship on one model but want to display the field on a form for the other model. How do I do this? for example: # classes class modelA(models.Model): name = models.CharField(max_length=300) manytomany = models.ManyToManyField(modelA) class modelB(models.Model): name = models.CharField(max_length=300) # forms class modelBForm(forms.ModelForm): class Meta: model = modelB I want to use the form modelBForm but show a select box with a list from modelA (just how it would work if the model was set to modelA in the form class). How can I do this? Thanks

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