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  • Core Data: migrating entities with self-referential properties

    - by Dan
    My Core Data model contains an entity, Shape, that has two self-referential relationships, which means four properties. One pair is a one-to-many relationship (Shape.containedBy <- Shape.contains) and the another is a many-to-many relationship (Shape.nextShapes <<- Shape.previousShapes). It all works perfectly in the application, so I don't think self-referencing relationships is a problem in general. However, when it comes to migrating the model to a new version, then Xcode fails to compile the automatically generated mapping model, with this error message: 2009-10-30 17:10:09.387 mapc[18619:607] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unable to parse the format string "FUNCTION($manager ,'destinationInstancesForSourceRelationshipNamed:sourceInstances:' , 'contains' , $source.contains) == 1"' *** Call stack at first throw: ( 0 CoreFoundation 0x00007fff80d735a4 __exceptionPreprocess + 180 1 libobjc.A.dylib 0x00007fff83f0a313 objc_exception_throw + 45 2 Foundation 0x00007fff819bc8d4 _qfqp2_performParsing + 8412 3 Foundation 0x00007fff819ba79d +[NSPredicate predicateWithFormat:arguments:] + 59 4 Foundation 0x00007fff81a482ef +[NSExpression expressionWithFormat:arguments:] + 68 5 Foundation 0x00007fff81a48843 +[NSExpression expressionWithFormat:] + 155 6 XDBase 0x0000000100038e94 -[XDDevRelationshipMapping valueExpressionAsString] + 260 7 XDBase 0x000000010003ae5c -[XDMappingCompilerSupport generateCompileResultForMappingModel:] + 2828 8 XDBase 0x000000010003b135 -[XDMappingCompilerSupport compileSourcePath:options:] + 309 9 mapc 0x0000000100001a1c 0x0 + 4294973980 10 mapc 0x0000000100001794 0x0 + 4294973332 ) terminate called after throwing an instance of 'NSException' Command /Developer/usr/bin/mapc failed with exit code 6 The 'contains' is the name of one of the self-referential properties. Anyway, the really big problem is that I can't even look at this Mapping Property as Xcode crashes as soon as I select the entity mapping when viewing the mapping model. So I'm a bit lost really where to go from here. I really can't remove the self-referential properties, so I'm thinking I've got manually create a mapping model that compiles? Any ideas? Cheers

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  • When is referential integrity not appropriate?

    - by Curtis Inderwiesche
    I understand the need to have referential integrity for limiting specific values on entry or possibly preventing them from removal upon a request of deletion. However, I am unclear as to a valid use case which would exclude this mechanism from always being used. I guess this would fall into several sub-questions: When is referential integrity not appropriate? Is it appropriate to have fields containing multiple and/or possibly incomplete subsets of a foreign key's list? Typically, should this be a schema structure design decision or an interface design decision? (Or possibly neither or both) Thoughts?

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  • Using Constraints on Hierarchical Data in a Self-Referential Table

    - by pbarney
    Suppose you have the following table, intended to represent hierarchical data: +--------+-------------+ | Field | Type | +--------+-------------+ | id | int(10) | | parent | int(10) | | name | varchar(45) | +--------+-------------+ The table is self-referential in that the parent_id refers to id. So you might have the following data: +----+--------+---------------+ | id | parent | name | +----+--------+---------------+ | 1 | 0 | fruit | | 2 | 0 | vegetable | | 3 | 1 | apple | | 4 | 1 | orange | | 5 | 3 | red delicious | | 6 | 3 | granny smith | | 7 | 3 | gala | +----+--------+---------------+ Using MySQL, I am trying to impose a (self-referential) foreign key constraint upon the data to update on cascades and prevent deletion of fruit if they have "children." So I used the following: CREATE TABLE `idtlp_main`.`fruit` ( `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT, `parent` INT(10) UNSIGNED, `name` VARCHAR(45) NOT NULL, PRIMARY KEY (`id`), CONSTRAINT `fk_parent` FOREIGN KEY (`parent`) REFERENCES `fruit` (`id`) ON UPDATE CASCADE ON DELETE RESTRICT ) ENGINE = InnoDB; From what I understand, this should fit my requirements. (And parent must default to null to allow insertions, correct?) The problem is, if I change the id of a record, it will not cascade: Cannot delete or update a parent row: a foreign key constraint fails (`iddoc_main`.`fruit`, CONSTRAINT `fk_parent` FOREIGN KEY (`parent`) REFERENCES `fruit` (`id`) ON UPDATE CASCADE) What am I missing? Feel free to correct me if my terminology is screwed up... I'm new to constraints.

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  • Referential Integrity: Best Practices for IBM DB2

    Of the various constraints possible on relational tables, referential constraints are perhaps the most common ... and most misused. Learn about the advantages and disadvantages of different methods to implement and enforce RI, and issues that must be addressed when implementing DBMS-enforced Referential Integrity.

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  • Database triggers / referential integrity and in-memory caching

    - by Ran Biron
    Do you see database triggers / referential integrity rules being used in a way that changes actual data in the database (changing row w in table x causes a change in row y in table z)? If yes, How does this tie-in with the increasing popularity of in-memory caching (memcache and friends)? After all, these actions occur inside the database but the caching system must be aware of them in order to reflect to correct state (or at least invalidate the possibly changed state). I find it hard to believe that callbacks are implemented for such cases. Does anyone have real-world experience with such a setup / real-world experience with considering such a setup and abandoning it (which way did you go? if caching, how do you enforce integrity?)

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  • Model self referential collections in Rails

    - by Najitaka
    I have written an application for an online clothing store in Rails 2.3.5. I want to show related Products when a customer views the Product Detail page. For example, if the customer views the detail page for a suit, I'd like to display the accessory products that match the dress such as a vest, shoes, and belt. I have named the related products an Ensemble. However, the vest, shoes, and belts are also Products which is what has me struggling. I have it working as follows but I know it's not the Rails way. I have a Products table for all of the products. Not important here but I also have a ProductDetails table. I have an Ensembles table that has the following columns: product_id - the main or origination product, the one displayed on the detail page outfit_id - the related or accessory product In setting up the data, on the Products list, for each Product I have an Ensemble link. This link takes you to the index action in the Ensembles controller. Using the id from the "main" Product, I find all of the associated Ensemble rows by product_id or I create a new ensemble and assign the id from the main product as the product_id. I'd like to just be able to do @product.related_products to get an Ensemble collection. Also on the index page I list the columns of the main product so the user can be sure their main product was the one they selected from the list. I also have a select list of the other products, with an Add to Ensemble action. Finally on the same index page, I have a table that displays the products that are already in the ensemble and in that list each row has a destroy link to remove a particular product from the ensemble. It would be nice if given a single Ensemble row @ensemble I could do @ensemble.product to get the Product related to the outfit_id of the ensemble row. I've got it working without associations but I have to run queries in the controller to build my own @product, @ensemble, and @ensembles collections. Also the only way I found to destroy an ensemble row is by Ensemble.connection.delete(sql to delete), simple @ensemble.destroy doesn't work. Anyone know how I would set up the associations or have a link to a site explaining a similar setup. None of the examples I found use the same table. They have A related to B through C. I want A related to other A through B.

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  • Sets, Surrogates, Normalisation, Referential Integrity - the Theory with example Scaling considerati

    - by tonyrogerson
    The Slides and Demo's for the SQLBits session I did today at SQL Bits in London are attached. The Agenda was... Thinking in Sets Surrogate Keys ú What they are ú Comparison NEWID, NEWSEQUENTIALID, IDENTITY ú Fragmenation Normalisation ú An introduction – what is it? Why use it? ú Joins – Pre-filter problems, index intersection ú Fragmentation again Referential Integrity ú Optimiser -> Query rewrite ú Locking considerations around Foreign Keys and Declarative RI (using Triggers)...(read more)

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  • Is it Possible to Use Constraints on Hierarchical Data in a Self-Referential Table?

    - by pbarney
    Suppose you have the following table, intended to represent hierarchical data: +--------+-------------+ | Field | Type | +--------+-------------+ | id | int(10) | | parent | int(10) | | name | varchar(45) | +--------+-------------+ The table is self-referential in that the parent_id refers to id. So you might have the following data: +----+--------+---------------+ | id | parent | name | +----+--------+---------------+ | 1 | 0 | fruit | | 2 | 0 | vegetable | | 3 | 1 | apple | | 4 | 1 | orange | | 5 | 3 | red delicious | | 6 | 3 | granny smith | | 7 | 3 | gala | +----+--------+---------------+ Using MySQL, I am trying to impose a (self-referential) foreign key constraint upon the data to cascade on update and prevent deletion of a record if it has any "children." So I used the following: CREATE TABLE `test`.`fruit` ( `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT, `parent` INT(10) UNSIGNED, `name` VARCHAR(45) NOT NULL, PRIMARY KEY (`id`), CONSTRAINT `fk_parent` FOREIGN KEY (`parent`) REFERENCES `fruit` (`id`) ON UPDATE CASCADE ON DELETE RESTRICT ) ENGINE = InnoDB; From what I understand, this should fit my requirements. (And parent must default to null to allow insertions, correct?) The problem is, if I change the id of a record, it will not cascade: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`fruit`, CONSTRAINT `fk_parent` FOREIGN KEY (`parent`) REFERENCES `fruit` (`id`) ON UPDATE CASCADE) What am I missing? Feel free to correct me if my terminology is screwed up... I'm new to constraints.

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  • How do I create a self referential association (self join) in a single class using ActiveRecord in Rails?

    - by Daniel Chang
    I am trying to create a self join table that represents a list of customers who can refer each other (perhaps to a product or a program). I am trying to limit my model to just one class, "Customer". The schema is: create_table "customers", force: true do |t| t.string "name" t.integer "referring_customer_id" t.datetime "created_at" t.datetime "updated_at" end add_index "customers", ["referring_customer_id"], name: "index_customers_on_referring_customer_id" My model is: class Customer < ActiveRecord::Base has_many :referrals, class_name: "Customer", foreign_key: "referring_customer_id", conditions: {:referring_customer_id => :id} belongs_to :referring_customer, class_name: "Customer", foreign_key: "referring_customer_id" end I have no problem accessing a customer's referring_customer: @customer.referring_customer.name ... returns the name of the customer that referred @customer. However, I keep getting an empty array when accessing referrals: @customer.referrals ... returns []. I ran binding.pry to see what SQL was being run, given a customer who has a "referer" and should have several referrals. This is the SQL being executed. Customer Load (0.3ms) SELECT "customers".* FROM "customers" WHERE "customers"."id" = ? ORDER BY "customers"."id" ASC LIMIT 1 [["id", 2]] Customer Exists (0.2ms) SELECT 1 AS one FROM "customers" WHERE "customers"."referring_customer_id" = ? AND "customers"."referring_customer_id" = 'id' LIMIT 1 [["referring_customer_id", 3]] I'm a bit lost and am unsure where my problem lies. I don't think my query is correct -- @customer.referrals should return an array of all the referrals, which are the customers who have @customer.id as their referring_customer_id.

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  • Problems Enforcing Referential Integrity on SQL Server Tables

    - by SidC
    Hello All, I have a SQL Server 2005 database comprised of Customer, Quote, QuoteDetail tables. I want/need to enforce referential integrity such that when an insert is made on quotedetail, the quote and customer tables are also affected. I have tried my best to set up primary/foreign keys on my tables but need some help. Here's the scripts for my tables as they stand now (please don't laugh): Customers: USE [Diel_inventory] GO /****** Object: Table [dbo].[Customers] Script Date: 05/08/2010 03:39:04 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[Customers]( [pkCustID] [int] IDENTITY(1,1) NOT NULL, [CompanyName] [nvarchar](50) NULL, [Address] [nvarchar](50) NULL, [City] [nvarchar](50) NULL, [State] [nvarchar](2) NULL, [ZipCode] [nvarchar](5) NULL, [OfficePhone] [nvarchar](12) NULL, [OfficeFAX] [nvarchar](12) NULL, [Email] [nvarchar](50) NULL, [PrimaryContactName] [nvarchar](50) NULL, CONSTRAINT [PK_Customers] PRIMARY KEY CLUSTERED ([pkCustID] ASC)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] Quotes: USE [Diel_inventory] GO /****** Object: Table [dbo].[Quotes] Script Date: 05/08/2010 03:30:46 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[Quotes]( [pkQuoteID] [int] IDENTITY(1,1) NOT NULL, [fkCustomerID] [int] NOT NULL, [QuoteDate] [timestamp] NOT NULL, [NeedbyDate] [datetime] NULL, [QuoteAmt] [decimal](6, 2) NOT NULL, [QuoteApproved] [bit] NOT NULL, [fkOrderID] [int] NOT NULL, CONSTRAINT [PK_Bids] PRIMARY KEY CLUSTERED ( [pkQuoteID] ASC)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[Quotes] WITH CHECK ADD CONSTRAINT [fkCustomerID] FOREIGN KEY([fkCustomerID]) REFERENCES [dbo].[Customers] ([pkCustID]) GO ALTER TABLE [dbo].[Quotes] CHECK CONSTRAINT [fkCustomerID] QuoteDetail: USE [Diel_inventory] GO /****** Object: Table [dbo].[QuoteDetail] Script Date: 05/08/2010 03:31:58 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[QuoteDetail]( [ID] [int] IDENTITY(1,1) NOT NULL, [fkQuoteID] [int] NOT NULL, [fkCustomerID] [int] NOT NULL, [fkPartID] [int] NULL, [PartNumber1] [float] NOT NULL, [Qty1] [int] NOT NULL, [PartNumber2] [float] NULL, [Qty2] [int] NULL, [PartNumber3] [float] NULL, [Qty3] [int] NULL, [PartNumber4] [float] NULL, [Qty4] [int] NULL, [PartNumber5] [float] NULL, [Qty5] [int] NULL, [PartNumber6] [float] NULL, [Qty6] [int] NULL, [PartNumber7] [float] NULL, [Qty7] [int] NULL, [PartNumber8] [float] NULL, [Qty8] [int] NULL, [PartNumber9] [float] NULL, [Qty9] [int] NULL, [PartNumber10] [float] NULL, [Qty10] [int] NULL, [PartNumber11] [float] NULL, [Qty11] [int] NULL, [PartNumber12] [float] NULL, [Qty12] [int] NULL, [PartNumber13] [float] NULL, [Qty13] [int] NULL, [PartNumber14] [float] NULL, [Qty14] [int] NULL, [PartNumber15] [float] NULL, [Qty15] [int] NULL, [PartNumber16] [float] NULL, [Qty16] [int] NULL, [PartNumber17] [float] NULL, [Qty17] [int] NULL, [PartNumber18] [float] NULL, [Qty18] [int] NULL, [PartNumber19] [float] NULL, [Qty19] [int] NULL, [PartNumber20] [float] NULL, [Qty20] [int] NULL, CONSTRAINT [PK_QuoteDetail] PRIMARY KEY CLUSTERED ( [ID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[QuoteDetail] WITH CHECK ADD CONSTRAINT [FK_QuoteDetail_Customers] FOREIGN KEY ([fkCustomerID]) REFERENCES [dbo].[Customers] ([pkCustID]) GO ALTER TABLE [dbo].[QuoteDetail] CHECK CONSTRAINT [FK_QuoteDetail_Customers] GO ALTER TABLE [dbo].[QuoteDetail] WITH CHECK ADD CONSTRAINT [FK_QuoteDetail_PartList] FOREIGN KEY ([fkPartID]) REFERENCES [dbo].[PartList] ([RecID]) GO ALTER TABLE [dbo].[QuoteDetail] CHECK CONSTRAINT [FK_QuoteDetail_PartList] GO ALTER TABLE [dbo].[QuoteDetail] WITH CHECK ADD CONSTRAINT [FK_QuoteDetail_Quotes] FOREIGN KEY([fkQuoteID]) REFERENCES [dbo].[Quotes] ([pkQuoteID]) GO ALTER TABLE [dbo].[QuoteDetail] CHECK CONSTRAINT [FK_QuoteDetail_Quotes] Your advice/guidance on how to set these up so that customer ID in Customers is the same as in Quotes (referential integrity) and that CustomerID is inserted on Quotes and Customers when an insert is made to QuoteDetial would be much appreciated. Thanks, Sid

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  • JPA2 adding referential contraint to table complicates criteria query with lazy fetch, need advice

    - by Quaternion
    Following is a lot of writing for what I feel is a pretty simple issue. Root of issue is my ignorance, not looking so much for code but advice. Table: Ininvhst (Inventory-schema inventory history) column ihtran (inventory history transfer code) using an old entity mapping I have: @Basic(optional = false) @Column(name = "IHTRAN") private String ihtran; ihtran is really a foreign key to table Intrnmst ("Inventory Transfer Master" which contains a list of "transfer codes"). This was not expressed in the database so placed a referential constraint on Ininvhst re-generating JPA2 entity classes produced: @JoinColumn(name = "IHTRAN", referencedColumnName = "TMCODE", nullable = false) @ManyToOne(optional = false) private Intrnmst intrnmst; Now previously I was using JPA2 to select the records/(Ininvhst entities) from the Ininvhst table where "ihtran" was one of a set of values. I used in.value() to do this... here is a snippet: cq = cb.createQuery(Ininvhst.class); ... In in = cb.in(transactionType); //Get in expression for transacton types for (String s : transactionTypes) { //has a value in = in.value(s);//check if the strings we are looking for exist in the transfer master } predicateList.add(in); My issue is that the Ininvhst used to contain a string called ihtran but now it contains Ininvhst... So I now need a path expression: this.predicateList = new ArrayList<Predicate>(); if (transactionTypes != null && transactionTypes.size() > 0) { //list of strings has some values Path<Intrnmst> intrnmst = root.get(Ininvhst_.intrnmst); //get transfermaster from Ininvhst Path<String> transactionType = intrnmst.get(Intrnmst_.tmcode); //get transaction types from transfer master In<String> in = cb.in(transactionType); //Get in expression for transacton types for (String s : transactionTypes) { //has a value in = in.value(s);//check if the strings we are looking for exist in the transfer master } predicateList.add(in); } Can I add ihtran back into the entity along with a join column that is both references "IHTRAN"? Or should I use a projection to somehow return Ininvhst along with the ihtran string which is now part of the Intrnmst entity. Or should I use a projection to return Ininvhst and somehow limit Intrnmst just just the ihtran string. Further information: I am using the resulting list of selected Ininvhst objects in a web application, the class which contains the list of Ininvhst objects is transformed into a json object. There are probably quite a few serialization methods that would navigate the object graph the problem is that my current fetch strategy is lazy so it hits the join entity (Intrnmst intrnmst) and there is no Entity Manager available at that point. At this point I have prevented the object from serializing the join column but now I am missing a critical piece of data. I think I've said too much but not knowing enough I don't know what you JPA experts need. What I would like is my original object to have both a string object and be able to join on the same column (ihtran) and have it as a string too, but if this isn't possible or advisable I want to hear what I should do and why. Pseudo code/English is more than fine.

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  • Build and render infinite hierarchical category tree from self-referential category table

    - by FreshCode
    I have a Categories table in which each category has a ParentId that can refer to any other category's CategoryId that I want to display as multi-level HTML list, like so: <ul class="tree"> <li>Parent Category <ul> <li>1st Child Category <!-- more sub-categories --> </li> <li>2nd Child Category <!-- more sub-categories --> </li> </ul> </li> </ul> Presently I am recursively rendering a partial view and passing down the next category. It works great, but it's wrong because I'm executing queries in a view. How can I render the list into a tree object and cache it for quick display every time I need a list of all hierarchical categories?

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  • Maintaining both sides of self-referential many-to-many relationship in Grails domain object

    - by Ali G
    I'm having some problems getting a many-to-many relationship working in grails. Is there anything obviously wrong with the following: class Person { static hasMany = [friends: Person] static mappedBy = [friends: 'friends'] String name List friends = [] String toString() { return this.name } } class BootStrap { def init = { servletContext -> Person bob = new Person(name: 'bob').save() Person jaq = new Person(name: 'jaq').save() jaq.friends << bob println "Bob's friends: ${bob.friends}" println "Jaq's friends: ${jaq.friends}" } } I'd expect Bob to be friends with Jaq and vice-versa, but I get the following output at startup: Running Grails application.. Bob's friends: [] Jaq's friends: [Bob] (I'm using Grails 1.2.0)

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  • Castle ActiveRecord - schema generation without enforcing referential integrity?

    - by Simon
    Hi all, I've just started playing with Castle active record as it seems like a gentle way into NHibernate. I really like the idea of the database schema being generate from my classes during development. I want to do something similar to the following: [ActiveRecord] public class Camera : ActiveRecordBase<Camera> { [PrimaryKey] public int CameraId {get; set;} [Property] public int CamKitId {get; set;} [Property] public string serialNo {get; set;} } [ActiveRecord] public class Tripod : ActiveRecordBase<Tripod> { [PrimaryKey] public int TripodId {get; set;} [Property] public int CamKitId {get; set;} [Property] public string serialNo {get; set;} } [ActiveRecord] public class CameraKit : ActiveRecordBase<CameraKit> { [PrimaryKey] public int CamKitId {get; set;} [Property] public string description {get; set;} [HasMany(Inverse=true, Table="Cameras", ColumnKey="CamKitId")] public IList<Camera> Cameras {get; set;} [HasMany(Inverse=true, Table="Tripods", ColumnKey="CamKitId")] public IList<Camera> Tripods {get; set;} } A camerakit should contain any number of tripods and cameras. Camera kits exist independently of cameras and tripods, but are sometimes related. The problem is, if I use createschema, this will put foreign key constraints on the Camera and Tripod tables. I don't want this, I want to be able to to set CamKitId to null on the tripod and camera tables to indicate that it is not part of a CameraKit. Is there a way to tell activerecord/nhibernate to still see it as related, without enforcing the integrity? I was thinking I could have a cameraKit record in there to indicate "no camera kit", but it seems like oeverkill. Or is my schema wrong? Am I doing something I shouldn't with an ORM? (I've not really used ORMs much) Thanks!

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  • Creating self-referential tables with polymorphism in SQLALchemy

    - by Jace
    I'm trying to create a db structure in which I have many types of content entities, of which one, a Comment, can be attached to any other. Consider the following: from datetime import datetime from sqlalchemy import create_engine from sqlalchemy import Column, ForeignKey from sqlalchemy import Unicode, Integer, DateTime from sqlalchemy.orm import relation, backref from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Entity(Base): __tablename__ = 'entities' id = Column(Integer, primary_key=True) created_at = Column(DateTime, default=datetime.utcnow, nullable=False) edited_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False) type = Column(Unicode(20), nullable=False) __mapper_args__ = {'polymorphic_on': type} # <...insert some models based on Entity...> class Comment(Entity): __tablename__ = 'comments' __mapper_args__ = {'polymorphic_identity': u'comment'} id = Column(None, ForeignKey('entities.id'), primary_key=True) _idref = relation(Entity, foreign_keys=id, primaryjoin=id == Entity.id) attached_to_id = Column(Integer, ForeignKey('entities.id'), nullable=False) #attached_to = relation(Entity, remote_side=[Entity.id]) attached_to = relation(Entity, foreign_keys=attached_to_id, primaryjoin=attached_to_id == Entity.id, backref=backref('comments', cascade="all, delete-orphan")) text = Column(Unicode(255), nullable=False) engine = create_engine('sqlite://', echo=True) Base.metadata.bind = engine Base.metadata.create_all(engine) This seems about right, except SQLAlchemy doesn't like having two foreign keys pointing to the same parent. It says ArgumentError: Can't determine join between 'entities' and 'comments'; tables have more than one foreign key constraint relationship between them. Please specify the 'onclause' of this join explicitly. How do I specify onclause?

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  • Java library to partially export a database while respecting referential integrity constraints

    - by Mwanji Ezana
    My production database is several GB's uncompressed and it's getting to be a pain to download and run locally when trying to reproduce a bug or test a feature with real data. I would like to be able to select the specific records that interest me, then have the library figure out what other records are necessary to produce a dataset that respects the databases integrity constraints and finally print it out as a list of insert statements or dump that I can restore. For example: given Author, Blog and Comment tables when I select comments posted after a certain date I should get inserts for the Blog records the comments have foreign keys to and the Author records those Blogs have foreign keys to.

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  • Self-referential ReferenceProperty in Google App Engine

    - by Ink-Jet
    I'm having a bit of trouble with ReferencePropertys in App Engine (Python). For a bit of fun, I'm trying to model a folder/file system, but having trouble getting folders to reference folders. My first attempt was this: class Folder(db.Model): id = db.StringProperty() name = db.StringProperty() created = db.DateTimeProperty(auto_now_add=True) folder = db.ReferenceProperty(Folder, collection_name="folders") But that fails as "Folder" isn't defined when "folder" is trying to be defined. I've also tried defining "folder" outside of the main declaration for "Folder", like so: class Folder(db.Model): id = db.StringProperty() name = db.StringProperty() created = db.DateTimeProperty(auto_now_add=True) Folder.folder = db.ReferenceProperty(Folder, collection_name="folders") But that fails with: AttributeError: 'Folder' object has no attribute 'folders' I'm kind of stumped. Does anyone have experience with this, or a solution to this problem? Thanks in advance.

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  • rails: self-referential association

    - by john
    hi, My needs are very simple: I have a Tip table to receive comments and have comments to receive comments, too. To retrieve each comment that is stored in the same table (comments), I created another key for the comments on comments: "inverse_comments". I tried to use one comments table by using self-referntial association. Some resources seem to bring more than one table into the piture which are diffent from my needs. So I came up whth the following modeling for comments: class Comment < ActiveRecord::Base belongs_to :tip belongs_to :user has_many :mycomments, :through => :inverse_comments, :source => :comment end Apparently something is missing here but I cannot figure it out. Could some one enlighten me on this: what changes I need to do to make the model work? thanks.

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  • mysql circular dependency in foreign key constraints

    - by Flavius
    Given the schema: What I need is having every user_identities.belongs_to reference an users.id. At the same time, every users has a primary_identity as shown in the picture. However when I try to add this reference with ON DELETE NO ACTION ON UPDATE NO ACTION, MySQL says #1452 - Cannot add or update a child row: a foreign key constraint fails (yap.#sql-a3b_1bf, CONSTRAINT #sql-a3b_1bf_ibfk_1 FOREIGN KEY (belongs_to) REFERENCES users (id) ON DELETE NO ACTION ON UPDATE NO ACTION) I suspect this is due to the circular dependency, but how could I solve it (and maintain referential integrity)?

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  • sql server db deployment script ignoring constraints etc until commit

    - by Daniel
    Hi all, I am planning on doing a database deployment script for sql server 2005. Currently we have a tool that will run all of the tables, foreign keys, indexes and then data, each of which is located in a separate file with a certain extension (eg. tab, .kci, .fky) and the tool just runs *.tab, *.kci, *.fky into the db etc. Could I possibly combine all of thse into one file and have them run ignoring referential integrity until they are all complete, I would turn it on before we started inserting test data. It is just unmanageable having to maintain 4 or 5 different types of scripts for one table. Are there any issues I should be aware of? Cheers

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  • Edit of self referencing HABTM in cakephp works, sometimes

    - by Odegard
    I'm using a self referencing HABTM model with Participants. You sign up for an event and when you log in to your reservation/profile you see a list of other participants and you can choose to add yourself and others into various groups; share hotel room, share transportation from airport etc. What I've managed so far: 1) In my profile I see the list of all other participants with checkboxes. Great so far. 2) Adding another participant works fine. Next time I edit, the participant I added is shown as checked. 3) Removing another participant works fine too as long as you still have checked participants before you submit! Again, with words: There are 3 participants. I'm logged in as one of them, and I see the 2 other people on the participants list. I choose to check both of them. This works fine (always). Later I choose to remove one of them (by unchecking the checkbox and hitting submit). This also works fine (always). If I want to remove the last checkbox... nothing is updated (always!). What's curious is that I can add and remove any odd combination of participants and it will always work UNLESS I choose to remove every participants in one go (removing a one and only participant is a special case of "remove all checked participants"). As far as I know, HABTMs work by first deleting all relations, then re-saving them. I can see that in my tables when I remove, add, remove, add the same participant over and over again - the id on the HABTM table is always increasing. When I deselect all participants at once, however, the relations are not updated. The ids stay the same, so it's like the save never happened. This behaviour is so specific and peculiar, I have a feeling I'm missing something obvious here. Anyway, here's the relevant code: Model class Participant extends AppModel { var $hasAndBelongsToMany = array( 'buddy' = array( 'className' = 'Participant', 'joinTable' = 'participants_participants', 'foreignKey' = 'participant_id', 'associationForeignKey' = 'buddy_id', 'unique' = true, ) ); Controller function edit($id = null) { if (!$id && empty($this-data)) { $this-Session-setFlash(__('Invalid Participant', true)); $this-redirect(array('action'='index')); } if (!empty($this-data)) { if ($this-Participant-saveAll($this-data)) { $this-Session-setFlash(__('The Participant has been saved', true)); $this-redirect(array('action'='index')); } else { $this-Session-setFlash(__('The Participant could not be saved. Please, try again.', true)); } } if (empty($this-data)) { $this-data = $this-Participant-read(null, $id); } // Fetching all participants except yourself $allParticipants = $this-Participant-find('list', array('conditions' = array('participant.id ' = $id))); // Fetching every participant that has added you to their list $allBuddies = $this-Participant-ParticipantsParticipant-find('list', array( 'conditions' = array('buddy_id' = $id), 'fields' = 'ParticipantsParticipant.participant_id', 'order' = 'ParticipantsParticipant.participant_id ASC' )); $this-set(compact('allParticipants','allBuddies')); } View echo $form-create('Participant'); echo $associations-habtmCheckBoxes($allParticipants, $this-data['buddy'], 'buddy', 'div', '\'border: 1px solid #000;\'', '\'border: 1px solid #000;\''); echo $form-end('Submit'); I'm using a slightly modified helper, habtmCheckBoxes, found here: http://cakeforge.org/snippet/detail.php?type=snippet&id=190 It works like this: function habtmCheckBoxes($rows=array(), $selectedArr=array(), $modelName, $wrapTag='p', $checkedDiv, $uncheckedDiv) {}

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  • Does SQL Server 2005 error message numbers back to the asp.net application?

    - by Duke
    I'd like to get the message number and severity level information from SQL Server upon execution of an erroneous query. For example, when a user attempts to delete a row being referenced by another record, and the cascade relationship is "no action", I'd like the application to be able to check for error message 547 ("The DELETE statement conflicted with the REFERENCE constraint...") and return a user friendly and localized message to the user. When running such a query directly on SQL Server, the following message is printed: Msg 547, Level 16, State 0, Line 1 <Error message...> In an Asp.Net app is this information available in an event handler parameter or elsewhere? Also, I don't suppose anyone knows where I can find a definitive reference of SQL Server message numbers?

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  • Modeling many-to-one with constraints?

    - by Greg Beech
    I'm attempting to create a database model for movie classifications, where each movie could have a single classification from each of one of multiple rating systems (e.g. BBFC, MPAA). This is the current design, with all implied PKs and FKs: TABLE Movie ( MovieId INT ) TABLE ClassificationSystem ( ClassificationSystemId TINYINT ) TABLE Classification ( ClassificationId INT, ClassificationSystemId TINYINT ) TABLE MovieClassification ( MovieId INT, ClassificationId INT, Advice NVARCHAR(250) -- description of why the classification was given ) The problem is with the MovieClassification table whose constraints would allow multiple classifications from the same system, whereas it should ideally only permit either zero or one classifications from a given system. Is there any reasonable way to restructure this so that a movie having exactly zero or one classifications from any given system is enforced by database constraints, given the following requirements? Do not duplicate information that could be looked up (i.e. duplicating ClassificationSystemId in the MovieClassification table is not a good solution because this could get out of sync with the value in the Classification table) Remain extensible to multiple classification systems (i.e. a new classification system does not require any changes to the table structure)? Note also the Advice column - each mapping of a movie to a classification needs to have a textual description of why that classification was given to that movie. Any design would need to support this.

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  • If some standards apply when "it depends" then should I stick with custom approaches?

    - by Travis J
    If I have an unconventional approach which works better than the industry standard, should I just stick with it even though in principal it violates those standards? What I am talking about is referential integrity for relational database management systems. The standard for enforcing referential integrity is to CASCADE delete. In practice, this is just not going to work all the time. In my current case, it does not. The alternative suggested is to either change the reference to NULL, DEFAULT, or just to take NO ACTION - usually in the form of a "soft delete". I am all about enforcing referential integrity. Love it. However, sometimes it just does not fully apply to use all the standards in practice. My approach has been to slightly abandon a small part of one of those practices which is the part about leaving "hanging references" around. Oops. The trade off is plentiful in this situation I believe. Instead of having deprecated data in the production database, a splattering of "soft delete" logic all across my controllers (and views sometimes depending on how far down the chain the soft delete occurred), and the prospect of queries taking longer and longer - instead of all that - I now have a recycle bin and centralized logic. The only tradeoff is that I must explicitly manage the possibility of "hanging references" which can be done through generics with one class. Any thoughts?

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