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  • Foreign Key Relationship in Rails

    - by Steve
    Hi...I am a beginner in Rails and I read that the Rails enforces the foreign key relationships at the model level and also at the database level in the migration file, while creating the table. Is it really necessary and what kind of advantage does it provide

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  • Sqlite / SQLAlchemy: how to enforce Foreign Keys?

    - by Nick Perkins
    The new version of SQLite has the ability to enforce Foreign Key constraints, but for the sake of backwards-compatibility, you have to turn it on for each database connection separately! sqlite> PRAGMA foreign_keys = ON; I am using SQLAlchemy -- how can I make sure this always gets turned on? What I have tried is this: engine = sqlalchemy.create_engine('sqlite:///:memory:', echo=True) engine.execute('pragma foreign_keys=on') ...but it is not working!...What am I missing?

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  • SQL DROP TABLE foreign key constraint

    - by Polly Hollanger
    If I want to delete all the tables in my database like this, will it take care of the foreign key constraint? If not, how do I take care of that first? GO IF OBJECT_ID('dbo.[Course]','U') IS NOT NULL DROP TABLE dbo.[Course] GO IF OBJECT_ID('dbo.[Student]','U') IS NOT NULL DROP TABLE dbo.[Student]

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  • Drop all foreign keys in a table

    - by trnTash
    I had this script which worked in sql server 2005 -- t-sql scriptlet to drop all constraints on a table DECLARE @database nvarchar(50) DECLARE @table nvarchar(50) set @database = 'dotnetnuke' set @table = 'tabs' DECLARE @sql nvarchar(255) WHILE EXISTS(select * from INFORMATION_SCHEMA.TABLE_CONSTRAINTS where constraint_catalog = @database and table_name = @table) BEGIN select @sql = 'ALTER TABLE ' + @table + ' DROP CONSTRAINT ' + CONSTRAINT_NAME from INFORMATION_SCHEMA.TABLE_CONSTRAINTS where constraint_catalog = @database and table_name = @table exec sp_executesql @sql END It does not work in SQL Server 2008. How can I easily drop all foreign key constraints for a certain table? Does anyone have a better script?

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  • How to switch 'default' sound device controlled by hardware keys in Xubuntu?

    - by Ruth
    I installed xubuntu-desktop on a 12.04 Ubuntu upgrade after finding Gnome3 lacking. I've mostly been happy, but I've found an odd and frustrating bug. My laptop has two sound 'outputs' - an HDMI-out plug I never use, and the onboard speakers/headphones. For some reason, the hardware keys have been mapped to the HDMI output, even if I set it as 'fallback' in pavucontrol, and notify-osd only displays changes in the HDMI output (though the panel indicator volume control controls onboard sound). I'd ideally like both hardware keys and notify-osd to be looking at the onboard sound, though if I can't get notify-osd it's an acceptable loss. Having to click through a bunch of stuff to change volume is driving me crazy, though. Googling suggested that it /may/ be a Pulseaudio/ALSA conflict, but the hardware keys seem to change at least indicated volume in pavucontrol for HDMI as expected (I don't have an HDMI cable to test actual sound output)

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  • not able to install signature keys

    - by Aman
    Hi , I have to sign an blackberry application so that i can load it to the device but, the signature keys i got from the RIM are installed on the system gets formatted and now i am trying to install the signature keys on another system but the server prompts me for this "Unable to register client'2909103544'because there are no more registration attempts.If you have already registered with this server,then you must contact RIM to register additional user" Can we install these keys to only single computer or now i had to purchase new keys

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  • Rails Foreign key setup question.

    - by James P. Wright
    I'm just (re)starting playing around with Rails and I'm making a little card game app. I cannot seem to figure out my Foreign Key setups. Say I have 4 objects: - Game - Player - Hand - Card A Game has many Players, which have many Hands which have many Cards. But the cards are also independent of a Hand, Player and Game. For example, I have 6 Cards in my database (1 to 6). It is possible that Card 3 could be in 2 Players Hands in the same Game. How can I set up my keys for this? Should I just create another object for "CardInHand" to simplify it?

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  • hibernate foreign key mapping many-to-one

    - by Lily
    I have been working on it for quite a while, but still can't figure out what's wrong with my code. Each Service has multiple profiles, but each profile only has one Service. Service { Long service_id; // primary key ... getter/setter } Profile { Long profile_id; // primary key Long service_id; // foreign key ... getter and setter } in Profile.hbm.xml. I add < many-to-one name="service_id" class="com.mot.diva.dto.Service" column="SERVICE_ID" cascade="save-update"> < /many-to-one> Is it the correct way to map it?

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  • MySQL primary/foreign key size?

    - by David
    I seem to see a lot of people arbitrarily assigning large sizes to primary/foreign key fields in their MySQL schemas, such as INT(11) and even BIGINT(20) as WordPress uses. Now correct me if I'm wrong, but even an INT(4) would support (unsigned) values up to over 4 billion. Change it to INT(5) and you allow for values up to a quadrillion, which is more than you would ever need, unless possibly you're storing geodata at NASA/Google, which I'm sure most of us aren't. Is there a reason people use such large sizes for their primary keys? Seems like a waste to me...

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  • MySQL : how to add foreign key

    - by garcon1986
    Hello, I have the following code in mysql. create table employee( e_id int(10) not null auto_increment, user_id int(10), usertype_id default 1, name varchar(50), primary key (e_id) ); create table relation( r_id int(10) not null auto_increment, user_id int(10) not null, usertype_id int(10) not null, interest_id int(10) not null, primary key (id) ); Firstly, i want user_id will have the same value as column e_id; And then, i want to add user_id and usertype_id as an unity in table relation as a foreign key for user_id and usertype_id in table employee. Do you know how to do that? Thanks a lot.

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  • Delete all records that have no foreign key constraints

    - by Rodney Burton
    I have a SQL 2005 table with millions of rows in it that is being hit by users all day and night. This table is referenced by 20 or so other tables that have foreign key constraints. What I am needing to do on a regular basis is delete all records from this table where the "Active" field is set to false AND there are no other records in any of the child tables that reference the parent record. What is the most efficient way of doing this short of trying to delete each one at a time and letting it cause SQL errors on the ones that violate constraints? Also it is not an option to disable the constraints and I cannot cause locks on the parent table for any significant amount of time.

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  • Filtering foreign keys with AJAX in Django admin

    - by cnobile
    I have most of this figured out already. I have AJAX returning the region/state/province when a country is selected. The correct foreign key is saved to the database, however, when the record is viewed afterwards the selected state is not shown in the select nor are any states for the selected country. I understand why this is happening as, the admin view is not aware of the relation between the state and the country. So here is the question. Is there a hook in the admin view that will allow me to load the correct states for the country and set the selected attribute on the option in the select tag? Or how can I override the admin view for any forms that require the country and region/state/province set? I am using jQuery and Djando-1.1. Thanks

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  • Django: Set foreign key using integer?

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

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  • MySQL foreign key constraints, cascade delete

    - by Cudos
    Hello. I want to use foreign keys to keep the integrity and avoid orphans (I already use innoDB). How do I make a SQL statment that DELETE ON CASCADE? Secondly, that using DELETE ON CASCADE. E.g. if I delete a category then it would delete products related to that category even though there are other categories related to those products. The pivot table "categories_products" creates a many-to-many relationship between the two other tables. categories - id (INT) - name (VARCHAR 255) products - id - name - price categories_products - categories_id - products_id

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  • How to handle Foreign Keys with Entity Framework

    - by Jack Marchetti
    I have two entities. Groups. Pools. A Group can create many pools. So I setup my Pool table to have a GroupID foreign key. My code: using (entity _db = new entity()) { Pool p = new Pool(); p.Name = "test"; p.Group.ID = "5"; _db.AddToPool(p); } This doesn't work. I get a null reference exception on p.Group. How do I go about creating a new "Pool" and associating a GroupID?

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  • Inverted function keys (F1-F12) on HP Pavilion dv4t

    - by The Electric Muffin
    (I know there have already been a lot of questions about this, but none of them mentioned the dv4t specifically.) I'm thinking about getting an HP Pavilion dv4t-4200 or -5100, but something that's really irritating me is that by default the function keys (F1-F12) are "inverted"—without holding the Fn key, the function keys do things like change the brightness, change or mute the volume, and switch to an external display. Only if you hold Fn will they actually produce F1, F2, etc. This is not how keyboards are supposed to work. Is there any way to disable this "feature" that has been verified to work on the HP Pavilion dv4t-4200 or HP Pavilion dv4t-5100? I don't want to buy this computer unless this is possible.

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  • Text selection CTRL+SHIFT+Cursor Keys?

    - by mark
    Hi, I'm used to this Windows behavior that using CTRL+SHIFT+Cursor Keys I can select text word-wise. CTRL+Cursor Keys jumps word-wise and I use that a lot in combination with SHIFT to select text. This seems to be a "Windows thing" because it just works in all application. Now turning to Ubuntu 10.04, it doesn't work. CTRL+SHIFT+Cursor Keys just behaves like CTRL+Cursor Keys, i.e. I jump between the words but I can't select them that way. Another gotcha: I use CTRL+Cursor Keys to move fast between words, press down SHIFT, release CTRL and move the Cursor Keys to select text char by char and it doesn't work either. I need to release both keys complete. Is there a way to enable this?

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  • ASP MVC C#: LINQ Foreign Key Constraint conflicts

    - by wh0emPah
    I'm having a problem with LINQ. I have 2 tables (Parent-child relation) Table1: Events (EventID, Description) Table2: Groups (GroupID, EventID(FK), Description) Now i want to create an Event an and a child. Event e = new Event(); e.Description = "test"; Datacontext.Events.InsertOnSubmit(event) Group g = new Group(); g.Description = "test2"; g.EventID = e.EventID; Datacontext.Groups.InsertOnSubmit(g); Datacontext.SubmitChanges(); When i debug, i can see that after inserting the event. the EventID has gotten a new value (auto increment). But when Datacontext.SubmitChanges(); gets called. I get the following exception "The INSERT statement conflicted with the FOREIGN KEY constraint ... I know this can be solved by creating a relation in the LINQ diagram between Events and groups. And then setting the entity itself. But i don't want to load the events everytime i ask a list of groups. All i need is some way that when inserting the group fails, the event insert won't be comitted in the database. Sorry if this is a bit unclear, My english isn't really good. Thanks in advance!

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  • Populating a foreign key table with variable user input

    - by Vincent
    I'm working on a website that will be based on user contributed data, submitted using a regular HTML form. To simplify my question, let's say that there will be two fields in the form: "User Name" and "Country" (this is just an example, not the actual site). There will be two tables in the database : "countries" and "users," with "users.country_id" being a foreign key to the "countries" table (one-to-many). The initial database will be empty. Users from all over the world will submit their names and the countries they live in and eventually the "countries" table will get filled out with all of the country names in the world. Since one country can have several alternative names, input like Chile, Chili, Chilli will generate 3 different records in the countries table, but in fact there is only one country. When I search for records from Chile, Chili and Chilli will not be included. So my question is - what would be the best way to deal with a situation like this, with conditions such that the initial database is empty, no other resources are available and everything is based on user input? How can I organize it in such way that Chile, Chili and Chilli would be treated as one country, with minimum manual interference. What are the best practices when it comes to normalizing user submitted data and is there a scientific term for this? I'm sure this is a common problem. Again, I used country names just to simplify my question, it can be anything that has possible different spellings.

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  • Multiple Foreign keys to a single table and single key pointing to more than one table

    - by user1216775
    I need some suggestions from the database design experts here. I have around six foreign keys into a single table (defect) which all point to primary key in user table. It is like: defect (.....,assigned_to,created_by,updated_by,closed_by...) If I want to get information about the defect I can make six joins. Do we have any better way to do it? Another one is I have a states table which can store one of the user-defined set of values. I have defect table and task table and I want both of these tables to share the common state table (New, In Progress etc.). So I created: task (.....,state_id,type_id,.....) defect(.....,state_id,type_id,...) state(state_id,state_name,...) importance(imp_id,imp_name,...) There are many such common attributes along with state like importance(normal, urgent etc), priority etc. And for all of them I want to use same table. I am keeping one flag in each of the tables to differentiate task and defect. What is the best solution in such a case? If somebody is using this application in health domain, they would like to assign different types, states, importances for their defect or tasks. Moreover when a user selects any project I want to display all the types,states etc under configuration parameters section.

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  • Some of my keys are automatically being pressed along with other keys

    - by Santosh
    History The last time when my computer shutdown was a power failure. Now some keys are automatically being pressed when I type something. The last thing I did to keyboard setting was adding a keyboard layout (on Ubuntu). What is happening Whenever I press c, xc is writeen s gives me sd d gives me sd e gives me we 2 gives me 23, So when I want @ it gives me @# 3 gives me 23 Pressing CAPS Lock gives me F3 and vice-versa. All other key are either working fine or I don't use them. I have two operating system Ubuntu and Windows, I use Windows very less and found this problem on Ubuntu, but as soon as I logged in to Windows (for checking) then I found that Windows has the same problem. Effects on my life This starts form the time of login, even I have problem in typing my password. Whenever I try to save any webpage, it is bookmarked automatically. Whenever I copy, it is cut automatically. I have to spend more than half of time correcting what I have typed. Note: Typing thisd quwesdtion wasd rweally a big pain to mwe.

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