composite-key

问题 I have just upgraded to the latest EF 4.1 code-first using NuGet and now I am receiving an error regarding my mapping. I have this class public class UserApplication { [Key, Column(Order = 0)] [DatabaseGenerated(DatabaseGeneratedOption.None)] public int UserId { get; set; } [Key, Column(Order = 1)] [DatabaseGenerated(DatabaseGeneratedOption.None)] public int ApplicationId { get; set; } [ForeignKey("ApplicationId")] public virtual Application Application { get; set; } public DateTime

问题 I have a composite primary key in 1 table in oracle. I want to create a foreign key for one table entry in my second table that references the composite primary key in the first table. I am getting the error ORA-02256. Any thoughts on how I can enter this? CREATE TABLE groupspersonx ( personid number, groupid number, CONSTRAINT pk_persongroupid PRIMARY KEY(personid, groupid) ); CREATE TABLE restrictedgroups ( groupid number, name varchar2(50), dateadded date, since date, notes varchar2(1024),

问题 I am using eclipselink for JPA . I have an entity, which has a composite key fabricated out of two fields. Following is my Embeddable primary key class' fields(members). @Embeddable public class LeavePK { @ManyToOne(optional = false) @JoinColumn(name = "staffId", nullable = false) private Staff staff; @Temporal(TemporalType.TIMESTAMP) private Calendar date; //setters and getters } My entity is going to hold leave data related to a staff, so I am trying to combine staff object and leave date

问题 Trying to save a row in a table that has a composite key (Long & Date) via Spring Data JPA. The Long part of the composite key is @GeneratedValue. But I'm getting the following error when doing a basic save() call: org.hibernate.id.IdentifierGenerationException: null id generated for:class com.bts.billing.domain.CashBatchPaymentHistoryDto The date is getting set manually prior to the save() and I've validated the sequencer exists in the database and is accessible. Entity @Entity @Table(name =

问题 Trying to save a row in a table that has a composite key (Long & Date) via Spring Data JPA. The Long part of the composite key is @GeneratedValue. But I'm getting the following error when doing a basic save() call: org.hibernate.id.IdentifierGenerationException: null id generated for:class com.bts.billing.domain.CashBatchPaymentHistoryDto The date is getting set manually prior to the save() and I've validated the sequencer exists in the database and is accessible. Entity @Entity @Table(name =

问题 public class UserBuilding { [Key, Column(Order = 0)] public int UserId { get; set; } [Key, Column(Order = 1)] public int BuildingId { get; set; } public int BuildingLevel { get; set; } } If I wanted to return all the different buildings that belong to a user, I would do the following: database.UserBuildings.Where(b => b.UserId == userId); My question is what if I wanted to return a specific building from a specific user? What would be the most 'efficient' way of doing this? Is there a better

问题 I have four entities that I would like to translate into database tables via code first fluent api (I'm using a model found at databaseanswers.org), but I'm not certain as to how. The problem I'm having is that SuggestedMenuId is being migrated across two different tables in a Composite key (MenuCourse and CourseRecipeChoice). Here's the message I'm getting: "One or more validation errors were detected during model generation: \tSystem.Data.Entity.Edm.EdmAssociationConstraint: : The number of

问题 create_table :categories_posts, :id => false do |t| t.column :category_id, :integer, :null => false t.column :post_id, :integer, :null => false end I have a join table (as above) with columns that refer to a corresponding categories table and a posts table. I wanted to enforce a unique constraint on the composite key category_id, post_id in the categories_posts join table. But Rails does not support this (I believe). To avoid the potential for duplicate rows in my data having the same

问题 I'm asking and answering my own question, but i'm not assuming i have the best answer. If you have a better one, please post it! Related questions: How to set a backreference from an @EmbeddedId in JPA hibernate mapping where embeddedid (?) JPA Compound key with @EmbeddedId I have a pair of classes which are in a simple aggregation relationship: any instance of one owns some number of instances of the other. The owning class has some sort of primary key of its own, and the owned class has a

问题 Is it necessary that composite-id should be mapped to class ?? can it be like this ? <composite-id> <key-property=..../> <key-property=..../> </composite-id> or should be <composite-id class=....> <key-property=..../> <key-property=..../> </composite-id> should that necessary that if we have composite key then that class should implement equals() and override() method ? 回答1: Hibernate needs to be able to compare and serialize identifiers. So the identifier class must be serializable, and