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  • how to model a many to many relationship

    - by Maulin
    Here is the scenario, Articles have many Comments Users can write many Comments for many Articles The comments table contains both user_id article_id as foreign keys My models are set up like so class User < ActiveRecord::Base has_many :comments has_many :articles, :through => :comments class Article < ActiveRecord::Base has_many :comments has_many :users, :through => :comments class Comment < ActiveRecord::Base belongs_to :users belongs_to :articles My routes.rb has the following code map.resources :articles, :has_many => :comments map.resources :users, :has_many => :comments which produces the following routes new_article_comment edit_article_comment new_user_comment edit_user_comment etc... This is not what I want (atleast not what I think I want), since comments must always be related to users and article, how can I get a route like so new_user_article_comment edit_user_article_comment Then I could just do new_user_article_comment_path([@user, @article]) to create a new comment

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  • Filtering forms in MS Access

    - by terence6
    I have a simple form showing products from my database. Each product has a foreign key to manufacturer_id . I would like to filter my form by manufacturer_id instead of default product_id. How I can do that ? I know I must create a macro. Also I've already created a query, that takes manufacturer's name as argument and returns manufacturer_id. So basically it should work in this way, that when I press 'Filter' button on my form, it runs macro that opens my query asking for manufacturer's name. And when the name is returned the whole form is filtered (so somewhere there should be comparison between manufacturer_id in product and that returned from query, but I can't manage to do that). I'm using access 2007. Model:

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  • Parent-Child relation while using object data source

    - by Saba
    Hello guys I am experiencing with a class generator I've written, which generates a class for each table in database with each table field as a property and such. Before that, I used to add a typed dataset to the project and add some tables to it. It automatically detected the relationship between tables and when I added a parent table as data source of a datagrid, I could add another datagrid and use the foreing key data member of it's bindingsource to fill it, and when someone moved the focus on parent datagrid, the data in child datagrid would change accordingly. Now that I have my classes, I add an object as data source for my 2 datagrids, but obviously it doesn't detect a parent child relation. But It'd really help if I could have that foreign key relation in my object datasources. Is there any way to have that relation in object datasource?

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  • How to SET tiggers 0 in MySQL?

    - by Grijesh Chauhan
    In my MySQL database I have some Triggers ON DELETE and ON INSERT. Some time I need to switched-off my some Triggers, And I have to DROP e.g. DROP TRIGGER IF EXISTS hostgroup_before_insert // and reinstall. Is there any shortcut to SET triggers hostgroup_before_insert = 0 like we have for foreign keys mysql> SELECT version(); +-------------------------+ | version() | +-------------------------+ | 5.1.61-0ubuntu0.10.10.1 | +-------------------------+ 1 row in set (0.00 sec) I am new learner and I could not find regarding this on web.

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  • Trying to modify a constraint in PostgresSQL

    - by MISMajorDeveloperAnyways
    Postgres is getting quite annoying lately. I have checked the documentation provided by Oracle and found a way to do this without dropping the table. Problem is, it errors out at modify as it does not recognize the keyword. Using EMS SQL Manager for PostgreSQL. Alter table public.public_insurer_credit MODIFY CONSTRAINT public_insurer_credit_fk1 deferrable, initially deferred; I was able to work around it by dropping the constraint using : ALTER TABLE "public"."public_insurer_credit" DROP CONSTRAINT "public_insurer_credit_fk1" RESTRICT; ALTER TABLE "public"."public_insurer_credit" ADD CONSTRAINT "public_insurer_credit_fk1" FOREIGN KEY ("branch_id", "order_id", "public_insurer_id") REFERENCES "public"."order_public_insurer"("branch_id", "order_id", "public_insurer_id") ON UPDATE CASCADE ON DELETE NO ACTION DEFERRABLE INITIALLY DEFERRED;

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  • How do I specify (1) an order and (2) a meaninful string representation for users in my Django application?

    - by David Faux
    I have a Django application with users. I have a model called "Course" with a foreign key called "teacher" to the default User model that Django provides: class Course(models.Model): ... teacher = models.ForeignKey(User, related_name='courses_taught') When I create a model form to edit information for individual courses, the possible users for the teacher field appear in this long select menu of user names. These users are ordered by ID, which is of meager use to me. How can I order these users by their last names? change the string representation of the User class to be "Firstname Lastname (username)" instead of "username"?

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  • Exploring search options for PHP

    - by Joshua
    I have innoDB table using numerous foreign keys, but we just want to look up some basic info out of it. I've done some research but still lost. 1) How can I tell if my host has Sphinx installed already? I don't see it as an option for table storage method (i.e. innodb, myisam). 2) Zend_Search_Lucene, responsive enough for AJAX functionality of millions of records? 3) Mirror my innoDB with a myisam? Make every innodb transaction end with a write to the myisam, then use 1:1 lookups? How would I do this automagically? This should make MyISAM ACID-compliant and free(er) from corruption no? 4) PostgreSQL fulltext queries don't even look like SQL to me wtf, I don't have time to learn a new SQL syntax I need noob options 5) ???????????????????? This is high volume site on a decently-equipped VPS Thanks very much for any ideas.

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  • mySQL & Relational databases: How to handle sharding/splitting on application level?

    - by Industrial
    Hi everybody, I have thought a bit about sharding tables, since partitioning cannot be done with foreign keys in a mySQL table. Maybe there's an option to switch to a different relational database that features both, but I don't see that as an option right now. So, the sharding idea seems like a pretty decent thing. But, what's a good approach to do this on a application level? I am guessing that a take-off point would be to prefix tables with a max value for the primary key in each table. Something like products_4000000 , products_8000000 and products_12000000. Then the application would have to check with a simple if-statement the size of the id (PK) that will be requested is smaller then four, eight or twelve million before doing any actual database calls. So, is this a step in the right direction or are we doing something really stupid?

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  • How to store and compare time-zone sensitive times

    - by Chad Moran
    I have a data structure where an entity has times stored as an int (minutes into the day) for fast comparison. The entity also has a Foreign Key reference back to a TimeZone table which contains the .NET CLR ID Name and it's Standard Time/Daylight Time acronyms. Since this information is stored as time-zone insensitive - I was wondering how in LINQ to SQL I could convert this into a UTC DateTime for comparison against other times that will be in UTC. Just to be clear this conversion has to be done server-side so that I can execute filtering on the SQL Server and not the client. I am using .NET 3.5 SP1 and SQL Server 2008.

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  • Database Design for One to One relationships

    - by Greelmo
    I'm trying to finalize my design of the data model for my project, and am having difficulty figuring out which way to go with it. I have a table of users, and an undetermined number of attributes that apply to that user. The attributes are in almost every case optional, so null values are allowed. Each of these attributes are one to one for the user. Should I put them on the same table, and keep adding columns when attributes are added (making the user table quite wide), or should I put each attribute on a separate table with a foreign key to the user table. I have decided against using the EAV model. Thanks!

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  • django forms from two tables referencial integrity

    - by dana
    i have a class named cv,and a class named university, and each user that completes his cv, should choose a University he studyes at. My problem is: one student can study at one or 2 or three universities, or may be a user that is not student. I need to take this data into a form, and i use ModelForm. The data from the Cv class, and from the University class in the same form, and the user can add one or more universities, or no university. (in the same form) How should i do it? Should i use ModelForm? if i have a foreign key in the CV class, and the user is not a student (so he is at zero universities), i may get an referencial integrity error. thanks a lot

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  • Injecting relationships in DBIx::Class

    - by Carl
    I have a handful of DBIx::Class::Core objects that model various database tables. For some of those models (those that have a 'queue' column), I have another class inject subs (basically, to 'move' the model object along it's queue states). I'd like to also have that class inject has_many relationships ala class($name)->has_many('queue_history','MySchema::Result::QueueHistory', { 'foreign.record_id'=>'self.id' }, { where => { type => $name }} ); but I can't seem to get the relationships to register properly (keep getting "No Such Relationship" errors - however, when calling the relationship method on the sources provides back the relationship). Any clues as to what's wrong?

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  • LINQ to SQl updating primary key field?

    - by Curtis White
    I have a linq to sql table/class that uses a GUID as both a primary key and as foreign key. This problem came up when factoring some code that previously worked. The exception generated is "Operation is not valid due to the current state of the object." The process I use is as such: aspnet_User user() = new aspnet_User(); aspnet_user.childTable = new childTable(); .. set some properties user.Insert() -> my custom method ... @ my custom method using (mycontext dc = new context() ) { user.childTable.ID = (Guid)myNewlyCreatedGuid; } The exception occurs on the assignment childTable.set_UserId().

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  • Trouble Getting a Locally Hosted Copy of the English Language Wiktionary to include the Translations Sections

    - by user1436026
    I used MWDumper - http://www.mediawiki.org/wiki/Mwdumper - to import the xml dump of the English Language Wiktionary (specifically the file named enwiktionary-20120930-pages-meta-current.xml,) to my local server. I have found that under the Translations section (on each page for each English word,) next to the name of each language where I should be able to see the definition in a foreign language, I instead see Template:Tø, Template:T+, or Template:T- and I am not sure why this is. As an experiment, I also used WikiTaxi - http://www.yunqa.de/delphi/doku.php/products/wikitaxi/index - with the exact same XML dump and did not have this problem when viewing under WikiTaxi.exe. I have been searching through mediawiki.org looking for the answer, but have so far not been successful. I appreciate your help

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  • DB2 Child Table - Auto Delete With Parent

    - by gamerzfuse
    I have a bit of a task before me. (DB2 Database) I need to create a table that will be a child table (is that what it is called in SQL?) I need it so that it has a foreign key constraint with my other table, so when the parent table is modified (record deleted) the child table also loses that record. Once I have the table, I also need to populate it with the data from the other table (if there is an easy way to UPDATE this). If you could point me in the right direction, this would help alot, as I do not even know what syntax to look for. Thanks in advance

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  • Java JPA @OneToMany neededs to reciprocate @ManyToOne?

    - by bguiz
    Create Table A ( ID varchar(8), Primary Key(ID) ); Create Table B ( ID varchar(8), A_ID varchar(8), Primary Key(ID), Foreign Key(A_ID) References A(ID) ); Given that I have created two tables using the SQL statements above, and I want to create Entity classes for them, for the class B, I have these member attributes: @Id @Column(name = "ID", nullable = false, length = 8) private String id; @JoinColumn(name = "A_ID", referencedColumnName = "ID", nullable = false) @ManyToOne(optional = false) private A AId; In class A, do I need to reciprocate the many-to-one relationship? @Id @Column(name = "ID", nullable = false, length = 8) private String id; @OneToMany(cascade = CascadeType.ALL, mappedBy = "AId") private List<B> BList; //<-- Is this attribute necessary? Is it a necessary or a good idea to have a reciprocal @OneToMany for the @ManyToOne? If I make the design decision to leave out the @OneToMany annotated attribute now, will come back to bite me further down.

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  • CakePHP: How can I disable auto-increment on Model.id?

    - by tomws
    CakePHP 1.3.0, mysqli I have a model, Manifest, whose ID should be the unique number from a printed form. However, with Manifest.id set as the primary key, CakePHP is helping me by setting up auto-increment on the field. Is there a way to flag the field via schema.php and/or elsewhere to disable auto-increment? I need just a plain, old primary key without it. The only other solution I can imagine is adding on a separate manifest number field and changing foreign keys in a half dozen other tables. A bit wasteful and not as intuitive.

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  • Will sharpening my sword eventually lead to it cutting my head off?

    - by Achilles
    Sharpening the sword: All I've read in the developer community suggests that I should keep learning and studying to become the best developer I can. This will make me better at my job and more valuable as an employee. Cutting my head off: However there seems to be an influx of cheap programming labor constantly coming int to the market(college, foreign countries, etc.) I was part of that influx when I graduated. So my question is, What is the likely outcome? Will there always be a job where a skilled-programmer(Grey-Beard) will have a place to work and contribute, or will he eventually price himself out of the market by having such great knowledge and skill?

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  • asp.net mvc dataannotation different table

    - by mazhar kaunain baig
    i have a lang table which is as a foreign key in the link table , The link can be in 3 languages meaning there will be 3 rows in the link table everytime i enter the record. i am using jquery tabs to enter the records in 3 languages . ok so what architecture i should follow for validation with datannotation attributes. i am using link to sql with 2010 vs. i will be creating link class with MetadataType so how will i handle for eg link name attribute 3 times.

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  • ModelName(django.contrib.auth.models.User) vs ModelName(models.Model)

    - by amr.negm
    I am developing a django project. I created some apps, some of those are related to User model, for instance, I have a feeds app that handles user feeds, and another app that deals with extra user data like age, contacts, and friends. for each of these, I created a table that should be connected to the User model, which I using for storing and authenticating users. I found two ways to deal with this issue. One, is through extending User model to be like this: ModelName(User): friends = models.ManyToMany('self') ..... Two, is through adding a foreign key to the new table like this: ModelName(models.Model): user = models.ForeignKey(User, unique=True) friends = friends = models.ManyToMany('self') ...... I can't decide which to use in which case. in other words, what are the core differences between both?

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  • select from multiple tables with different columns

    - by Qaiser Iftikhar
    Say I got this sql schema. Table Job: id,title, type, is_enabled Table JobFileCopy: job_id,from_path,to_path Table JobFileDelete: job_id, file_path Table JobStartProcess: job_id, file_path, arguments, working_directory There are many other tables with varying number of columns and they all got foreign key job_id which is linked to id in table Job. My questions: Is this the right approach? I don't have requirement to delete anything at anytime. I will require to select and insert mostly. Secondly, what is the best approach to get the list of jobs with relevant details from all the different tables in a single database hit? e.g I would like to select top 20 jobs with details, their details can be in any table (depends on column type in table Job) which I don't know until runtime. Thanks in advance. Regards,

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  • Best way to model Customer <--> Address

    - by Jen
    Every Customer has a physical address and an optional mailing address. What is your preferred way to model this? Option 1. Customer has foreign key to Address Customer (id, phys_address_id, mail_address_id) Address (id, street, city, etc.) Option 2. Customer has one-to-many relationship to Address, which contains a field to describe the address type Customer (id) Address (id, customer_id, address_type, street, city, etc.) Option 3. Address information is de-normalized and stored in Customer Customer (id, phys_street, phys_city, etc. mail_street, mail_city, etc.) One of my overriding goals is to simplify the object-relational mappings, so I'm leaning towards the first approach. What are your thoughts?

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  • Disable Primary Key and Re-Enable After SQL Bulk Insert

    - by Jon
    I am about to run a massive data insert into my DB. I have managed to work out how to enable and rebuild non-clustered indexes on my tables but I also want to disable/enable primary keys. You can't disable the clustered index for the primary key as the table is inaccessible when that is done and my attempt to do a ALTER TABLE for constraints does not work as I think that is only for foreign keys. Do you know of a way to Disable the Primary Key and Re-Enable After SQL Bulk Insert. NOTE: This is over numerous tables and so I don't know the exact primary key specifications eg/name etc

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  • copy child collection to another object

    - by Bogdan
    Hi everyone, I have a one-to-many relationship between Part and Params (a "Part" has many "Params). I'm trying to do something naive like this: Part sourcePart = em.find(Part.class, partIdSource); Part destPart = em.find(Part.class, partIdDest); Collection<Param> paramListSource = sourcePart.getParamList(); destPart.setParamList(paramListSource); Basically I want to copy all the parameters from sourcePart to destPart. Hopefully the persistence provider will automatically set the right foreign keys in the Param table/entity. The above code will obviously not work. Is there any easy way of doing this, or do I have to do create a new collection, then add each Param (creating new Param, setting attributes, etc) ?

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  • Design ideas for a versioned db schema with related tables also versioned

    - by vfilby
    Here is the drill, I want to version a database. I have done this before using multiple rows where the table primary key becomes a combination of the row id and either a datestamp or a version #. Now I want to version a table that depends on many other small tables. Versioning each table will be a giant PITA, so I am looking for good options to verion a schema where the data to be versioned spreads over multiple tables. All related tables are properly keyed with foreign key relationships. The database is currently on Sql Server 2005.

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