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  • Django: many-to-one fields and data integrity

    - by John
    Let's say that I have a Person who runs an inventory system. Each Person has some Cars, and each Car has a very large number of Parts (thousands, let's say). A Person, Bob, uses a Django form to create a Car. Now, Bob goes to create some Parts. It is only at the form level that Django knows that the Parts belong to some specific Car, and that the Parts.ForeignKey(Car) field should only have a specific Car as a choice. When creating a Part, you have to mess with the form's constructor or similar in order to limit the choice of Cars to only the cars owned by Bob. It does not seem proper that to enforce this ownership at the form level. It seems that other users' Cars must be inaccessible to anyone but the owner of the Car. What do you all think about this, and is there any way to enforce this?

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  • Need to find latitude and longitude of postcodes and store into my database

    - by Matt
    Hey guys, Ive got a database full of UK Postcodes, now i'd like to be able to store the latitude and longitude of these specific postcodes along with the record with the database. Is there anyway that i can obtain this data free without violating any T&C's? I know i could do this using google maps api for each postcode, but i have way over 20,000 postcodes in this database and to get the lat and lng for each of these postcodes each time is not an option really. Thanks in advance, M

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  • MySQL efficiency as it relates to the database/table size

    - by mlissner
    I'm building a system using django, Sphinx and MySQL that's very quickly becoming quite large. The database currently has about 2000 rows, and I've written a program that's going to populate it with another 40,000 rows in a couple days. Since the database is live right now, and since I've never had a database with this much information in it, I'm worried about some things: Is adding all these rows going to seriously degrade the efficiency of my django app? Will I need to go back through it and optimize all my database calls so they're doing things more cleverly? Or will this make the database slow all around to the extent that I can't do anything about it at all? If you scoff at my 40k rows, then, my next question is, at what point SHOULD I be concerned? I will likely be adding another couple hundred thousand soon, so I worry, and I fret. How is sphinx going to feel about all this? Is it going to freak out when it realizes it has to index all this data? Or will it be fine? Is this normal for it? If it is, at what point should I be concerned that it's too much data for Sphinx? Thanks for any thoughts.

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  • Conditional relation

    - by Lowgain
    I've got a model like this: Stem -id -etc And then I have Stemrelation -stem_id -related_stem_id -active I can get the related stems with the following relations class Stem < ActiveRecord::Base has_many :stemrelations has_many :related_stems, :through => :stemrelations end class Stemrelation < ActiveRecord::Base belongs_to :stem belongs_to :related_stem, :class_name => "Stem", :foreign_key => "related_stem_id" end But now I'd only like to get the active relations. I tried adding this to the Stem model: has_many :active_related, :through => :stemrelations, :source => :related_stem, :conditions => {:active => true} but this gives me an error becasue it tries to check the active flag on the stem model instead of the stemrelation. What do I change here? Thanks!

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  • How to save big "database-like" class in python

    - by Rafal
    Hi there, I'm doing a project with reasonalby big DataBase. It's not a probper DB file, but a class with format as follows: DataBase.Nodes.Data=[[] for i in range(1,1000)] f.e. this DataBase is all together something like few thousands rows. Fisrt question - is the way I'm doing efficient, or is it better to use SQL, or any other "proper" DB, which I've never used actually. And the main question - I'd like to save my DataBase class with all record, and then re-open it with Python in another session. Is that possible, what tool should I use? cPickle - it seems to be only for strings, any other? In matlab there's very useful functionality named save workspace - it saves all Your variables to a file that You can open at another session - this would be vary useful in python!

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  • what's a good way to synchronize a sql server 2008 database from a 2005 database automatically?

    - by Keith Nicholas
    Ok, the scenario is... two servers, on completely different parts of the internet. The sql 2008 database just needs to get data updates and schema changes. It doesn't need to send anything to the 2005 database. Basically just suck data and schema as efficiently as possible automatically as a scheduled task. The database is quite huge.... but the changes per day are probablly around 20/30 megabytes of data/ I can't run any of the inbuilt replication on the 2005 database. I've had a wee look at the Sync Framework, I think that might do what I want, but seems a bit painful and requires a bit of work to get going. I'm wondering if there is tooling out there to make this easier? or?? not quite sure what my options are.

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  • Opening read-only OLEDB connection to MS Access back-end database while allowing updates via separat

    - by djdilicious
    I have a back-end MS Access 2002-2003 database which stores blog entries. I created a separate front-end database with the forms for entering blog posts into the backend database. Finally, I have a website utilizing ASP to display the blog entries. The website connects directly to the backend database using an OLEDB connection object. Whenever I open the form for creating a new post in MS Access, loading the blog post page on the website displays the error: Could not use "; file already in use. I would like to be able to display the older blog posts even though the newest one is in the process of being added.

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  • How to associate static entity instances in a Session without database retrieval

    - by Michael Hedgpeth
    I have a simple Result class that used to be an Enum but has evolved into being its own class with its own table. public class Result { public static readonly Result Passed = new Result(StatusType.Passed) { Id = [Predefined] }; public static readonly Result NotRun = new Result(StatusType.NotRun) { Id = [Predefined] }; public static readonly Result Running = new Result(StatusType.Running) { Id = [Predefined] }; } Each of these predefined values has a row in the database at their predefined Guid Id. There is then a failed result that has an instance per failure: public class FailedResult : Result { public FailedResult(string description) : base(StatusType.Failed) { . . . } } I then have an entity that has a Result: public class Task { public Result Result { get; set; } } When I save a Task, if the Result is a predefined one, I want NHibernate to know that it doesn't need to save that to the database, nor does it need to fetch it from the database; I just want it to save by Id. The way I get around this is when I am setting up the session, I call a method to load the static entities: protected override void OnSessionOpened(ISession session) { LockStaticResults(session, Result.Passed, Result.NotRun, Result.Running); } private static void LockStaticResults(ISession session, params Result[] results) { foreach (var result in results) { session.Load(result, result.Id); } } The problem with the session.Load method call is it appears to be fetching to the database (something I don't want to do). How could I make this so it does not fetch the database, but trusts that my static (immutable) Result instances are both up to date and a part of the session?

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  • rails: has_many :through validation?

    - by ramonrails
    Rails 2.1.0 (Cannot upgrade for now due to several constraints) I am trying to achieve this. Any hints? A project has many users through join model A user has many projects through join model Admin class inherits User class. It also has some Admin specific stuff. Admin like inheritance for Supervisor and Operator Project has one Admin, One supervisor and many operators. Now I want to 1. submit data for project, admin, supervisor and operator in a single project form 2. validate all and show errors on the project form. Project has_many :projects_users ; has_many :users, :through => :projects_users User has_many :projects_users ; has_many :projects, :through => :projects_users ProjectsUser = :id integer, :user_id :integer, :project_id :integer, :user_type :string ProjectUser belongs_to :project, belongs_to :user Admin < User # User has 'type:string' column for STI Supervisor < User Operator < User Is the approach correct? Any and all suggestions are welcome.

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  • Check for Duplicates in a Database Before Entering Data

    - by gamerzfuse
    Before Entering data into a database, I just want to check that the database doesn't have the same username in the database already. I have the username in SQL set as a key, so it can't be duplicated on that end, but I am looking at finding a more user-friendly error message then "KEY already exists". Is there are simple way to check if the variable value already exists in a row? Thanks!

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  • Hibernate overriding database modifications with detached object state

    - by EugeneP
    I'm gonna go with this design: create an object and keep it alive during all web-app session. And I need to synchronize its state with database state. What I want to achieve is that : IF between my db operations, that is, modifications that I persist to a db someone intentionally spoils table rows, then on next saving to a database all those changes WOULD BE OVERWRITTEN with the object state, that always contains valid data. What Hibernate methods do you recommend me to use to persist the modifications in a database? saveOrUpdate() is a possible solution, but maybe there's anything better? Again, I repeat how it looks. First I create an object without collections. Persist it (save()). Then user provides us with additional data. In a serviceLayer, again, we modify our object in memory (say, populate it with collections) and then, persist it again. So every serviceLayer operation of the next step must simply guarantee that database contains the exact persistent copy of this object that we have in memory. If data in a database differ, it MUST BE OVERRIDDEN with the object (kept in memory) state. What Session operations do you recommend?

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  • Issue in Adding data into database using hibernate

    - by sarah
    Hi , I am getting the following exception "org.hibernate.HibernateException: The database returned no natively generated identity value "while adding data into database i am using the following code.Please let me know what is wrong Sesion session=HibernateUtil.getSession(); Transaction tx = session.beginTransaction(); session.save(user); logger.info("Successfully data insert in database"); tx.commit(); isSaved=true; Thankx

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  • has_many through a habtm relationship in Rails

    - by macek
    I'm trying to define a has_many X, :through => Y where Y is a habtm relationship. Rails is throwing a fit about this. See comment in user model: class User < ActiveRecord::Base has_many :posts # I want to display a list of all tags this user is involved in has_many :tags, :through => :posts # ERROR end class Post < ActiveRecord::Base has_and_belongs_to_many :tags end class Tag < ActiveRecord::Base has_and_belongs_to_many :posts end What can I do to fix this?

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  • SQL: How do I INSERT primary key values from two tables INTO a master table.

    - by Stefan
    Hello, I would appreciate some help with an SQL statement I really can't get my head around. What I want to do is fairly simple, I need to take the values from two different tables and copy them into an master table when a new row is inserted into one of the two tables. The problem is perhaps best explained like this: I have three tables, productcategories, regioncategories and mastertable. --------------------------- TABLE: PRODUCTCATEGORIES --------------------------- COLUMNS: CODE | DESCRIPTION --------------------------- VALUES: BOOKS | Books --------------------------- --------------------------- TABLE: REGIONCATEGORIES --------------------------- COLUMNS: CODE | DESCRIPTION --------------------------- VALUES: EU | European Union --------------------------- --------------------------- TABLE: MASTERTABLE --------------------------- COLUMNS: REGION | PRODUCT --------------------------- VALUES: EU | BOOKS --------------------------- I want the values to be inserted like this when a new row is created in either productcategories or regioncategories. New row is created. --------------------------- TABLE: PRODUCTCATEGORIES --------------------------- COLUMNS: CODE | DESCRIPTION --------------------------- VALUES: BOOKS | Books --------------------------- VALUES: DVD | DVDs --------------------------- And a SQL statement copies the new values into the mastertable. --------------------------- TABLE: MASTERTABLE --------------------------- COLUMNS: REGION | PRODUCT --------------------------- VALUES: EU | BOOKS --------------------------- VALUES: EU | DVD --------------------------- The same goes if a row is created in the regioncategories. New row. --------------------------- TABLE: REGIONCATEGORIES --------------------------- COLUMNS: CODE | DESCRIPTION --------------------------- VALUES: EU | European Union --------------------------- VALUES: US | United States --------------------------- Copied to the mastertable. --------------------------- TABLE: MASTERTABLE --------------------------- COLUMNS: REGION | PRODUCT --------------------------- VALUES: EU | BOOKS --------------------------- VALUES: EU | DVD --------------------------- VALUES: US | BOOKS --------------------------- VALUES: US | DVD --------------------------- I hope it makes sense. Thanks, Stefan

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  • Sql script, create a database

    - by Blanca
    Hi! I have the next file: create_mysql.sql DROP DATABASE IF EXISTS playence_media; CREATE DATABASE playence_media; USE playence_media; GRANT ALL PRIVILEGES ON . TO 'media'@'localhost' IDENTIFIED BY 'media' WITH GRANT OPTION; But I don't know how to create this database. I would like to do it with my terminal, no other graphics interfaces. Thanks

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  • .NET TDD with a Database and ADO.NET Entity Framework - Integration Tests

    - by Brian
    Hello, I'm using ADO.NET entity framework, and am using an AdventureWorks database attached to my local database server. For unit testing, what approaches have people taken to work with a database? Obviously, the database has to be in a pre-defined state of change so that the tests can have some isolation from each other... so I need to be able to run through the inserts and updates, then rollback either between tests or after the batch of tests are done. Any advice? Thanks.

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  • What is the "owning side" in an ORM mapping?

    - by Yousui
    Hi guys, I'm new to JPA. Now I have a question that what exactly is the owning side mean? I only have a rough idea of it. Can someone give me an explanation with some mapping examples(one to many, one to one, many to one) please? Great thanks. ps, the following text is excerpt from the decription of @OneToOne in java EE 6 documentation. You can see the concept owning side in it. Defines a single-valued association to another entity that has one-to-one multiplicity. It is not normally necessary to specify the associated target entity explicitly since it can usually be inferred from the type of the object being referenced. If the relationship is bidirectional, the non-owning side must use the mappedBy element of the OneToOne annotation to specify the relationship field or property of the owning side.

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  • Connecting To SQL Database In C#

    - by Soo
    Hey everyone, I'm pretty familiar with SQL syntax (via MySQL) and am just getting my feet wet with C# and SQL server. I currently have a .sdf database on my C:\ drive and want to connect to it in C#. I added the database as a data source and now need help figuring out how to get data from the database in my C# application. I just want to be able to set an object to the data in my SQL database so I can manipulate it using C#. Thanks in advance for replies.

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  • Sqlite Database Firefox

    - by user159972
    Hi, I want to create a Sqlite Database in Firefox (I can update my Firefox). According to my knowledge Firefox does not give you Sqlite Database access. Is there any plugin or simple patch which gives Sqlite database simulation in Firefox? Regards, Allahbaksh

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  • A table that has relation to itself issue

    - by Mostafa
    Hi , I've defined table with this schema : CREATE TABLE [dbo].[Codings]( [Id] [int] IDENTITY(1,1) NOT NULL, [ParentId] [int] NULL, [CodeId] [int] NOT NULL, [Title] [nvarchar](50) COLLATE Arabic_CI_AI NOT NULL, CONSTRAINT [PK_Codings] PRIMARY KEY CLUSTERED ( [Id] ASC )WITH (IGNORE_DUP_KEY = OFF) ON [PRIMARY] ) ON [PRIMARY] And fill it up with data like this : Id ParentId CodeId Title ----------- ----------- ----------- ---------- 1 NULL 0 Gender 2 1 1 Male 3 1 2 Female 4 NULL 0 Educational Level 5 4 1 BS 6 4 2 MS 7 4 3 PHD Now , I'm looking for a solution , in order , When i delete a record that is parent ( like Id= 1 or 4 ), It delete all child automatically ( all records that their ParentId is 1 or 4 ) . I supposed i can do it via relation between Id and Parent Id ( and set cascade for delete rule ) , But when i do that in MMS , the Delete Rule or Update Rule in Properties is disabled . My question is , What can i do to accomplish this ? Thank you

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  • How do I left join tables in unidirectional many-to-one in Hibernate?

    - by jbarz
    I'm piggy-backing off of http://stackoverflow.com/questions/2368195/how-to-join-tables-in-unidirectional-many-to-one-condition. If you have two classes: class A { @Id public Long id; } class B { @Id public Long id; @ManyToOne @JoinColumn(name = "parent_id", referencedColumnName = "id") public A parent; } B - A is a many to one relationship. I understand that I could add a Collection of Bs to A however I do not want that association. So my actual question is, Is there an HQL or Criteria way of creating the SQL query: select * from A left join B on (b.parent_id = a.id) This will retrieve all A records with a Cartesian product of each B record that references A and will include A records that have no B referencing them. If you use: from A a, B b where b.a = a then it is an inner join and you do not receive the A records that do not have a B referencing them. I have not found a good way of doing this without two queries so anything less than that would be great. Thanks.

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  • Shrink database after removing extra data

    - by Sergey Osypchuk
    We have a need to fit database in 4G in order to use ms sql express edition. I started from 7G database, and found a lot of not needed records, and deleted them. After Shrink database size is 4.6G, and 748MB is free (according to database properties). However, when i execute exec sp_spaceused i am having interesting results: DatabaseName Database_size unallocation space xxxxxx 4726.50 MB 765.42 MB Reserved Data index_size unused 3899472 KB 1608776 KB 1448400 KB 842296 KB Any ideas, how can i bite at least some of this unused space? Also I know table, which occupied it. update: is it worth to try to rebuild table indexes? ALTER INDEX ALL ON Production.Product REBUILD

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  • mongoid with rails - Database should be a Mongo::DB, not NilClass"

    - by Adam T
    Greetings I am trying to get Mongoid to work with my Rails app and I am getting an error: "Mongoid::Errors::InvalidDatabase in 'Shipment bol should be unique' Database should be a Mongo::DB, not NilClass" I have created the mongoid.yml file in my config directory and have mongodb running as a daemon. The config file is like so: defaults: &defaults host: localhost development: <<: *defaults database: ship-it-development test: <<: *defaults database: ship-it-test production: <<: *defaults host: <%= ENV['MONGOID_HOST'] % port: <%= ENV['MONGOID_PORT'] % database: <%= ENV['MONGOID_DATABASE'] % All of my specs fail with the above error. I am using rails 2.3.8. Anyone have ideas?

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