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• SQL - Dervied Foreign Key - Possible?

  - by Chad

  I'm just curious if this is possible, specifically in SQL CE (Express) with support in .NET's Entity Framework: Table1 (primary) -nvarchar(2000) url -... Table2 (with foreign key) -nvarchar(2000) domain -... foreign key on Table2.domain references Table1.url such that Table.url contains Table2.domain e.g. Table1: http://www.google.com/blah/blah http://www.cnn.com/blah/ http://www.google.com/foo Table2: google.com cnn.com Is it possible for this to be scripted and enforced by SQL CE (let alone any relation database) and, if so, can .NET's Entity Framework automatically support this if I import my database into a model?

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• What is a good solution to link different tables in Hibernate based on some field value?

  - by serg555

  I have article table and several user tables a_user, b_user, ... with exactly the same structure (but different data). I can't change anything in *_user tables except their table name prefix but can change everything else (user tables contain only user information, there is nothing about article or user_type in them). I need to link article to a user (many-to-one), but user table name is defined by user_type field. For example Article table record: ... user_id="5" user_type="a" means that it is linked to a user with id=5 from a_user table (id 5 is not unique in users scope, each user table can have its id 5). Any suggestions how to handle this situation? How can I map this relation in Hibernate (xml mapping, no annotations) so it will automatically pick up correct user for an article during select/update? How should I map user tables (one or multiple classes?)? I would need to run some queries like this: from Article a where a.userType=:type and a.user.name=:name Thanks.

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• Help with a algorithm in linq to resolve a query

  - by Deumber

  I have been some time thinking how to resolve this problem, but out of ideas i prefer expose it for help. I have 2 tables (linq to sql) A and B, A have a many relation with B, so A have a property EntitySet of B A have the following properties: CreateDate (Datetime) ModificateDate (Datetime) Bs (EntitySet<B>) B have the following properties: CreateDate (Datetime) ModificateDate (Datetime) All that i want is return a ordered collection of A by the Max date between : A.CreateDate, A.ModificateDate, The Max B.CreateDate of all B in A The Max B.ModificateDate of all B in A if i someone need a little example, just ask for it.

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• using setSfGuardUser() to save the current user in the model

  - by user334017

  My application makes use of the sfGuardUser plugin. One of my tables has a relation onto the sf_guard_user table so there is a corresponding setSfGuardUser() function in the base model. From Actions.class.php, I am attempting to set the current user into the object using this function, (Which I then save in the database). my attempt: ->setSfGuardUser($this->getUser()); //called from inside Actions.class.php this throws an error: Couldn't call Doctrine_Core::set(), second argument should be an instance of Doctrine_Record or Doctrine_Null when setting one-to-one references. ...# at Doctrine_Record->coreSetRelated('sfGuardUser', object('myUser')) Which makes me think that getUser() is not returning a sfGuardUser object, though I don't know how to check this. Can anyone offer any insight?

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• NHibernate SchemaUpdate adding existing foreign keys again?

  - by afsharm

  I'm using SchemaUpdate to synchronize my hbms with existing database. Database has recently created based on hbms and is completely up-to-date. But SchemaUpdate generates all foreign key constraints again. For example suppose you have Student and Teacher. Student has association to Teacher with name ArtTeacher. ArtTeacher is a foreign key from Student to Teacher. Suppose database is up-to-date and currently holde Student, Teacher and their foreign key relation. So HBM and Database are equivalent. Know SchemaUpdate must not do anything but when I see its generated scripts, it re-produce that foreign key again. Why this happens? Is there any way to avoid it?

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• ManyToManyField error when having recursive structure. How to solve it?

  - by luc

  Hello, I have the following table in the model with a recursive structure (a page can have children pages) class DynamicPage(models.Model): name = models.CharField("Titre",max_length=200) parent = models.ForeignKey('self',null=True,blank=True) I want to create another table with manytomany relation with this one: class UserMessage(models.Model): name = models.CharField("Nom", max_length=100) page = models.ManyToManyField(DynamicPage) The generated SQL creates the following constraint: ALTER TABLE `website_dynamicpage` ADD CONSTRAINT `parent_id_refs_id_29c58e1b` FOREIGN KEY (`parent_id`) REFERENCES `website_dynamicpage` (`id`); I would like to have the ManyToMany with the page itself (the id) and not with the parent field. How to modify the model to make the constraint using the id and not the parent? Thanks in advance

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• I can't understand GroupJoin where i will need it in database relationships.

  - by Freshblood

  Hello Everybody I am thinking 5-6 hours to understand something about GroupJoin. I am talking about query with linq for Database tables.I understand what Join and GroupJoin does but I really couldn't understand where i will need it.I feel that Join does all what i will need but if there is something which Join can't without GroupJoin so i feel that situation is meaningless or useless. For example: Persons table in relation with Phones and Phones table hold foreign keys of Persons and one person can have one more phone number.If we want to brings all persons who has phone numbers and who hasn't too so we will need GroupJOin but what for we will need this query ? Can u give me good reason , example or explenation for using GroupJoin ?

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• find users that are following other users

  - by Jakob

  Hi I'm wondering how I can go about this problem I have a DB with a Users Table, and a Followers table. The Followers table contains 2 Columns "FollowerID" and "FollowedID" I have a 1 - * relation in my datamodel between Users.ID -> Followers.FollowerID and Users.ID -> FollowedID How do I in LINQ get a set of users that are following a specific user? I'll express what I'm trying to achieve programatically I can get this far: ctx.Followers.Where(f => f.FollowedID == CurrentUser.ID) so now i have a Followers set where I have the ID of the users that follow the CurrentUser, and I could iterate through this collection and then add users after each iteration to a collection that would be a total USER collection that followed CurrentUser, but isn't there a smarter, or LINQ'er way to do this? Much appreciated Thx

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• How to implement message passing in GNUradio?

  - by xuandl

  I need to implement message passing, my idea is to make some sort of message source (I inherit from public gr_sync_block) that works as a controller for another block (it has to send a message each 6 minutes). I read that is necessary to inherit from gnuradio::block -and by the way, installing grextras is mandatory-. In the .h file I added the #include and inherited from block"class JDFM_API jdfm_control : public gr_sync_block, public gnuradio::block". I know that I have redefine some things like the gnuradio::block constructor but I dont know what msg_signature is, I also don't get the relation between block's parameters and work parameter, the last thing that I am not sure is if I still can use gnuradio-companion if I create a block like this. I haven't been able to find a simple example of messages implementation. If anyone can guide me or show me an example, it would be awesome. Thanks in advance.

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• Sqlalchemy: Many to Many relationship error

  - by 1001010101

  Dear everyone, I am following the Many to many relationship described on http://www.sqlalchemy.org/docs/mappers.html#many-to-many #This is actually a VIEW tb_mapping_uGroups_uProducts = Table( 'mapping_uGroups_uProducts', metadata, Column('upID', Integer, ForeignKey('uProductsInfo.upID')), Column('ugID', Integer, ForeignKey('uGroupsInfo.ugID')) ) tb_uProducts = Table( 'uProductsInfo', metadata, Column('upID', Integer, primary_key=True) ) mapper( UnifiedProduct, tb_uProducts) tb_uGroupsInfo = Table( 'uGroupsInfo', metadata, Column('ugID', Integer, primary_key=True) ) mapper( UnifiedGroup, tb_uGroupsInfo, properties={ 'unifiedProducts': relation(UnifiedProduct, secondary=tb_mapping_uGroups_uProducts, backref="unifiedGroups") }) where the relationship between uProduct and uGroup are N:M. When I run the following sess.query(UnifiedProduct).join(UnifiedGroup).distinct()[:10] I am getting the error: sqlalchemy.exc.ArgumentError: Can't find any foreign key relationships between 'uProductsInfo' and 'uGroupsInfo' What am I doing wrong?

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• Why does the assignment operator return a value and not a reference?

  - by Nick Lowman

  I saw the example below explained on this site and thought both answers would be 20 and not the 10 that is returned. He wrote that both the comma and assignment returns a value, not a reference. I don't quite understand what that means. I understand it in relation to passing variables into functions or methods i.e primitive types are passed in by value and objects by reference but I'm not sure how it applies in this case. I also understand about context and the value of 'this' (after help from stackoverflow) but I thought in both cases I would still be invoking it as a method, foo.bar() which would mean foo is the context but it seems both result in a function call bar(). Why is that and what does it all mean? var x = 10; var foo = { x: 20, bar: function () {return this.x;} }; (foo.bar = foo.bar)();//returns 10 (foo.bar, foo.bar)();//returns 10

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• doctrine default values and relations

  - by Skirmantas

  Concept: Lets say we have table Properties with columns id and name (lets say with some predefined values: "Good" "Better" "Best"). Another table Users has column property_id with many to one relation on Properties (property_id = id). Users has default value on property_id, lets say 1 which means "Good". We might have another table analogue to Users however with default property, lets say "Better". What I need is ability to change default value for Users or other tables in administrator's panel. In mysql I can set default value for column like this: ALTER TABLE <Table> CHANGE <Column> DEFAULT <NEW_DEFAULT_VALUE> I can retrieve default value: SELECT DEFAULT(<Column>) FROM <Table> LIMIT 1 Is it possible to achieve this concept with Doctrine? What I actually need is such method in my table class: class UserTable extend Doctrine_Table { /* ... */ getDefaultProperty() { } setDefaultProperty($value) { /* $value can be either integer or Doctrine_Record */ } }

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• Why Resource (.resx) file added on merely changing Form size and on adding button which is not resou

  - by Muhammad Kashif Nadeem

  1- Resource files suppose to be added on adding some resource in application like image or audio or video etc. But if I just change size of form a .resx file under that particular form. Changing size of form does not add any resource so why this .resx file. 2- I dropped a button on form and a resource file is included again this button is not some kind of resource, it is object created and having information in designer file. 3- A resource file added on dropping button on form but if I delete this resource file and run application it compile and run with NO error and button is still there. If this button has any relation with resource file then there must by some kind of compile or runtime error AND if .resx file has nothing to do with button then why it was added? I am using VS 2008. Thanks in advance for the help

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• How to get the app a Django model is from?

  - by e-satis

  I have a model with a generic relation: TrackedItem --- genericrelation ---> any model I would like to be able to generically get, from the initial model, the tracked item. I should be able to do it on any model without modifying it. To do that I need to get the content type and the object id. Getting the object id is easy since I have the model instance, but getting the content type is not: ContentType.object.filter requires the model (which is just content_object.__class__.__name__) and the app_label. I have no idea of how to get in a reliable way the app in which a model is. For now I do app = content_object.__module__.split(".")[0], but it doesn't work with django contrib apps.

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• How can i pass an object to a new thread generated anonymously in a button listener

  - by WaterBoy

  I would like to pass an object (docket for printing) to a new thread which will print the docket. My code is: private final Button.OnClickListener cmdPrintOnClickListener = new Button.OnClickListener() { public void onClick(View v) { new Thread(new Runnable() { public void run() { enableTestButton(false); Looper.prepare(); doConnectionTest(); Looper.loop(); Looper.myLooper().quit(); } }).start(); } }; How do I pass the object to it? Also - I need to generate the object in the UI thread, just before starting the new thread so where could I put this method (e.g. getDocketObject()) in relation to my code below thanks, anton

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• Desgining a database with flexible user profile

  - by Mughrabi

  Hi, Am working on a design where I can have flexible attributes for a user & am confused how to continue the design of the schema. I made a table where I kept system needed information called users id username password Now, I wish to create a profile table and have one to one relation where all the other attributes in profile table such as email, first name, last name..etc. My question is, is there a way to add a third table in which even profile will be flexible if my clients need to create a new attribute he/she won't need any customization to the code? Regards,

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• With paperclip, how can I change the image location to a ":parent_model_id/:id" folder format?

  - by Jamis Charles

  Given that I have a Listing model that has many images and each image has one attachment, how can I have the listing_id be part of the folder structure? Like so: system/photos/[listing_id]/:id I know that using :id will output the id of the image record. Here's what I currently have: class Image < ActiveRecord::Base belongs_to :listing #Rails ActiveRecord Relation. An image belongs to a post. # paperclip data has_attached_file :photo, :styles => { :medium => "300x300>", :thumb => "100x100>" }, :url => "/public/system/:class/:attachment/:id/:style_:filename" end

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• Using Multiple Databases

  - by sergiuoala

  A company is hired by another company for helping in a certain field. So I created the following tables: Companies: id, company name, company address Administrators: (in relation with companies) id, company_id, username, email, password, fullname Then, each company has some workers in it, I store data about workers. Hence, workers has a profession, Agreement Type signed and some other common things. Now, the parent tables and data in it for workers (Agreement Types, Professions, Other Common Things) are going to be the same for each company. Should I create 1 new database for each company? Or store All data into the same database? Thanks.

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• Find record whose field 'name' not contained within any other record

  - by charlie

  I have a model Foo with a String bar and a String name. Some records' bar contain the name of other records in them. This is intentional. I want to find the "root Foo" records - that is, the ones where their name do not appear in the bar records of any other Foo records. Example: Foo id: 1 name: 'foo1' bar: 'something something' id: 2 name: 'foo2' bar: 'foo1 something' id: 3 name: 'foo3' bar: 'foo1, foo4' My method root_foos would return foo2 and foo3 since their names do not appear in any bar string. edit: I don't want to use a relation or foreign key here - just this method.

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• Understanding Eager Loading & How to use it? (specific issue)

  - by Elliot

  I have the following relation in my rails app: genre - has many - authors authors - belong to genre and has many books books - belongs to authors and belongs to users (users can add books to the db) in my controller I have: @books=current_user.books(:include => [:author => :genre], :order => 'books.created_at DESC')--- -- In my controller I used to have: @authors = Author.All @genres = Genre.All etc. -- In my view I have @genres.each do |genre| @authors.each do |author| if author.genre_id == genre.id stuff end end end Now that I'm using eager loading, I can't imagine this is the best way to do this (nor does it work as I don't have the @ variables) - I was wondering if anyone could shed some light on how to approach this?

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• MySQL is there a Single Select to Query Various Unrelated Values from a database?

  - by zzapper

  I saw somewhere what seemed to be nested selects, one "master" select on the "outside" and a series of selects inside- is this possible? I'm not talking about joins as there is particular relation between the selects. I seem not to be explaining myself very well. I want to do a single query which will pull out a series of stats from various tables latest order, latest customer, largest order. Obviously I can do that with a series of selects. The example I saw was something like select ( select ... from tbl_1 where .., select ... from tbl_2 where .., select ... from tbl_3 where .., ... )

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• Towards HEATMAP representation - R -

  - by user3710390

  I am trying to plot a simple heatmap of some data distribution in R. My data = matrix (5000 x3( Time , Complexity, Localisation )). Time ( 0- 7000) Cmplx (0-4) Localisation (1-15). i.e Time Cmplx Localisation 567 3 1 54 0 2 345 3 12 567 4 12 345 2 9 989 4 7 ... ... ... The idea is to plot the Time in relation to each Cmplx and each Localisation (Something like accumarray in mathlab) Have someone an idea? Thanks in advance, Guillon_

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• Django GenericRelation doesn't save related object's id - is this a bug or am I doing it wrong?

  - by pinkeen

  I have a model with a generic relation (call it A), when creating an instance of this object I pass an instance of another model (call it B) as the initializer of the content_object field (via kwargs of the constructor). If I don't save B before creating A then when saving A the content_object_id is saved to the db as NULL. If I save B before passing it to the constructor of A then everything's allright. It's not logical. I assumed that the ID of the related object (B) is fetched when doing A.save() and it should throw some kind of an exception if B isn't saved yet but it just fails silently. I don't like the current solution (saving B beforhand) because we don't know yet if I will be always willing to keep the object, not just scrap it, and there are performance considerations - what if I will add some another data and save it once more shortly after. class BaseNodeData(models.Model): ... extnodedata_content_type = models.ForeignKey(ContentType, null=True) extnodedata_object_id = models.PositiveIntegerField(null=True) extnodedata = generic.GenericForeignKey(ct_field='extnodedata_content_type', fk_field='extnodedata_object_id') class MarkupNodeData(models.Model): raw_content = models.TextField() Suppose we do: markup = MarkupNodeData(raw_content='...') base = BaseNodeData(..., extnodedata=markup) markup.save() base.save() # both records are inserted to the DB but base is stored with extnodedata_object_id=NULL markup = MarkupNodeData(raw_content='...') base = BaseNodeData(..., extnodedata=markup) base.save() markup.save() # no exception is thrown and everything is the same as above markup = MarkupNodeData(raw_content='...') markup.save() base = BaseNodeData(..., extnodedata=markup) base.save() # this works as expected Of course I can do it this way, but it doesn't change anything: base = BaseNodeData(...) base.extnodedata = markup My question is - is this a bug in django which I should report or maybe I'm doing something wrong. Docs on GenericRelations aren't exactly verbose.

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• One database or many?

  - by dsims

  I am developing a website that will manage data for multiple entities. No data is shared between entities, but they may be owned by the same customer. A customer may want to manage all their entities from a single "dashboard". So should I have one database for everything, or keep the data seperated into individual databases? Is there a best-practice? What are the positives/negatives for having a: database for the entire site (entity has a "customerID", data has "entityID") database for each customer (data has "entityID") database for each entity (relation of database to customer is outside of database) Multiple databases seems like it would have better performance (fewer rows and joins) but may eventually become a maintenance nightmare.

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• SQL most popular

  - by Brae

  I have a mysql table with items in relation to their order. CREATE DATABASE IF NOT EXISTS `sqltest`; USE `sqltest`; DROP TABLE IF EXISTS `testdata`; CREATE TABLE `testdata` ( `orderID` varchar(10) DEFAULT NULL, `itemID` varchar(10) DEFAULT NULL, `qtyOrdered` int(10) DEFAULT NULL, `sellingPrice` decimal(10,2) DEFAULT NULL ) INSERT INTO `testdata`(`orderID`,`itemID`,`qtyOrdered`,`sellingPrice`) values ('1','a',1,'7.00'),('1','b',2,'8.00'),('1','c',3,'3.00'),('2','a',1,'7.00'),('2','c',4,'3.00'); Intended Result: A = (1+1)2 B = 2 C = (2+4)6 <- most popular How do I add up all the qty's for each item and result the highest one? It should be fairly strait forward but I'm new to SQL and I can't work this one out :S Solution needs to be mysql and or php. I guess there needs to be some sort of temporary tally variable for each item ID, but that seems like it could get messy with too many items.

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