one-to-one | 易学教程

@OneToOne bidirectional mapping with @JoinColumn

阅读更多关于 @OneToOne bidirectional mapping with @JoinColumn

问题 Let's say I have Person class Person{ @Id Integer id; @OneToOne @JoinColumn(name = "person_id") Job myJob; } and Job class Job{ @Id Integer id; Integer person_id; @OneToOne @PrimaryKeyJoinColumn(name = "person_id") Person currentWorker; } I'm not able to map the Person and Job to other Entity, when fetching. What mistake am I doing ? 回答1: Your code should be: @Entity public class Person implements Serializable { @Id Integer id; @OneToOne @JoinColumn(name = "id") Job myJob; } @Entity public

ModelForm with OneToOneField in Django

阅读更多关于 ModelForm with OneToOneField in Django

问题 I have two models in Django that are related with a OneToOneField ( PrinterProfile and PrinterAdress ). I am trying to do a form with PrinterProfileForm , but for some reason it does NOT pass the PrinterAddress fields into the form (it's not rendered by Django "magic" in the template). What should I do so that my PrinterProfileForm include as well the fields from PrinterAddress (its related OneToOneField )? Thanks a lot class PrinterProfile(TimeStampedModel): user = models.OneToOneField(User)

Java: Hibernate @OneToOne mapping

阅读更多关于 Java: Hibernate @OneToOne mapping

问题 I\'m trying to get Hibernate @OneToOne annotations working and not having much success here... Let\'s say I\'ve got a table called status that looks like this: +------------------------------------------------+ | status | +------------------------------------------------+ | id | frn_user_id | frn_content_id | status | +----+-------------+----------------+------------+ | 1 | 111 | 0 | \"active\" | +----+-------------+----------------+------------+ | 2 | 0 | 222 | \"inactive\" | +----+---------

One to one optional relationship using Entity Framework Fluent API

阅读更多关于 One to one optional relationship using Entity Framework Fluent API

We want to use one to one optional relationship using Entity Framework Code First. We have two entities. public class PIIUser { public int Id { get; set; } public int? LoyaltyUserDetailId { get; set; } public LoyaltyUserDetail LoyaltyUserDetail { get; set; } } public class LoyaltyUserDetail { public int Id { get; set; } public double? AvailablePoints { get; set; } public int PIIUserId { get; set; } public PIIUser PIIUser { get; set; } } PIIUser may have a LoyaltyUserDetail but LoyaltyUserDetail must have a PIIUser . We tried these fluent approach techniques. modelBuilder.Entity<PIIUser>()

Hibernate: one-to-one lazy loading, optional = false

阅读更多关于 Hibernate: one-to-one lazy loading, optional = false

I faced the problem that one-to-one lazy loading doesn't work in hibernate. I've already solved it , but still don't properly understand what happens. My code ( lazy loading doesn't work here , when I pull Person - Address is also fetched): @Entity public class Person{ @Id @SequenceGenerator(name = "person_sequence", sequenceName = "sq_person") @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "person_sequence") @Column(name = "id") private long personID; @OneToOne(mappedBy="person", cascade=CascadeType.ALL, fetch = FetchType.LAZY) private Adress address; //.. getters, setters }

How do I create a real one-to-one relationship in SQL Server

阅读更多关于 How do I create a real one-to-one relationship in SQL Server

I want to create a one-to-one relationship in SQL Server 2008 R2. I have two tables tableA and tableB , I set tableB 's primary key as foreign key which references tableA 's primary. But when I use Entity Framework database-first, the model is 1 to 0..1. Any one know how to create real 1 to 1 relationship in database? Erik Philips I'm pretty sure it is technically impossible in SQL Server to have a True 1 to 1 relationship, as that would mean you would have to insert both records at the same time (otherwise you'd get a constraint error on insert), in both tables, with both tables having a

Why use a 1-to-1 relationship in database design?

阅读更多关于 Why use a 1-to-1 relationship in database design?

问题 I am having a hard time trying to figure out when to use a 1-to-1 relationship in db design or if it is ever necessary. If you can select only the columns you need in a query is there ever a point to break up a table into 1-to-1 relationships. I guess updating a large table has more impact on performance than a smaller table and I\'m sure it depends on how heavily the table is used for certain operations (read/ writes) So when designing a database schema how do you factor in 1-to-1

EF Code First - 1-to-1 Optional Relationship

阅读更多关于 EF Code First - 1-to-1 Optional Relationship

问题 I want to map an optional 1-to-1 relationship in an existing database with EF Code First. Simple schema: User Username ContactID Contact ID Name Obviously ContactID joins to Contact.ID. The ContactID field is nullable so the relationship is optional - 0 or 1, never many. So how do I specify this relationship in EF Code First, with this existing schema? Here\'s what I\'ve tried so far: public class User { [Key] public string Username { get; set; } public int? ContactID { get; set; }

JPA @OneToOne with Shared ID — Can I do this Better?

阅读更多关于 JPA @OneToOne with Shared ID — Can I do this Better?

问题 I’m working with an existing schema that I’d rather not change. The schema has a one-to-one relationship between tables Person and VitalStats, where Person has a primary key and VitalStats uses the same field as both its primary key and its foreign key to Person, meaning its value is the value of the corresponding PK of Person. These records are created by external processes, and my JPA code never needs to update VitalStats. For my object model I’d like my Person class to contain a VitalStats

How to declare one to one relationship using Entity Framework 4 Code First (POCO)

阅读更多关于 How to declare one to one relationship using Entity Framework 4 Code First (POCO)

问题 How to declare a one to one relationship using Entity Framework 4 Code First (POCO)? I found this question (one-to-one relationships in Entity Framework 4) , but the article that the answer references was not useful (there is one line of code that is a 1-1 relationship, but no mention of how to define it). 回答1: Are you just looking for something like this? public class User { public int Id { get; set; } public string Username { get; set; } public Profile Profile { get; set; } public int