one-to-one

问题 I can't see any difference in the schema of a Many-To-One relationship vs a OneToOne relationship: @Entity public class Order { @ManyToOne @JoinColumn(nullable = false) private Address address; vs @Entity public class Order { @OneToOne @JoinColumn(nullable = false) private Address address; Is there any difference? 回答1: They look exactly the same on schema but there is difference on Hibernate Layer. If you try something like that: Address address = new Address(); Order order1 = new Order();

问题 I have 2 classes: User and UserPicture which have a 1:1 relationship. public class User { @Id @GeneratedValue(strategy=GenerationType.AUTO) @Column(name="id", nullable = false, unique = true) private int id; private String firstname; private String lastname; @OneToOne @JoinColumn(name = "picture") //field named "picture" in the database private UserPicture userPicture; .. } public class UserPicture { @Id @GeneratedValue(strategy=GenerationType.AUTO) @Column(name="id", nullable = false, unique

问题 I have a Joke model: class Joke(models.Model): ... date_created = models.DateTimeField(default=datetime.now, blank=True) date_modified = models.DateTimeField(default=datetime.now, blank=True) creator = models.OneToOneField(User, default=1) Now, when I try to migrate the last line I get errors. Basically, I want to link a User to the Joke object, and since I already have a database, I want the default value to be 1, which is the admin user's id(I checked...). Makemigrations works just fine but

问题 How to get and set entity witch onetoone relation like my example. I have error : Entity of type Miejsce\ObiektyBundle\Entity\UsersInformatio n is missing an assigned ID for field ' user_id '. The identifier generation strategy for this entity requires the ID field to be populated before EntityManager#persist() is called. If you want automatically generated identifiers instead you need to adjust the metadata mapping accordingly. in php controller - i try save new item in this way: $product =

问题 I know a lot of people is asking about one-to-one relationships on EF 4.1 but I can't seem to find an answer for this problem. I have these POCO classes: public class Contact { public decimal nCont_id { get; set; } public virtual WebsiteMembership WebsiteMembership { get; set; } //a bunch of other properties } public class WebsiteMembership { public int WebsiteMembershipId { get; set; } public virtual Contact Contact { get; set; } } Website membership's primary key (WebsiteMembershipId) is

问题 I am creating my first JPA based project. My application features several tables with foreign key relationships for integrity purposes. Many related tables are normalized lookup tables. Consider the tables Person and Account , having a fk relationship on accountid : +-Person----+ | personid | +-Account---+ | accountid*|==============>| accountid | | ... | | ... | +-----------+ +-----------+ In the front end (JSF), I created a form for new Person objects containing a selectOneMenu list with

问题 I need to create a table EMPLOYEE_REMARK from a table EMPLOYEE. And need to do it with Annotation Hibernate. EMPLOYEE EMP_ID, EMP_FNAME, EMP_LNAME EMPLOYEE_REMARK EMP_REMARK_ID, EMP_ID, REMARK it will be a OnetoOne relationship i.e, for each EMP_ID there will be one REMARK. REMARK could be null. please help me with the solution... Can it be done by creating one class from employee and populate the EMPLOYEE_REMARK from it??? 回答1: Basically here is the way of doing what you want. Employee

问题 Is there a way to prevent Doctrine from assigning a contraint on both sides of a one-to-one relationship? Ive tried moving the definition from one side to the other and using owning side but it still places a constraint on both tables. when I only want the parent table to have a constraint - ie. its possible for the parent to not have an associated child. For example iwant the following sql schema essentially: CREATE TABLE `parent_table` ( `child_id` varchar(50) NOT NULL, `id` integer

问题 I want to have custom join query for OneToOne relationships. I need to add one more clause to where part, because without it I get More than one row with the given identifier was found: com.example.Container_$$_javassist_0@17156065, for class: com.example.AnyContainer Is it possible to do that? Container.java @Entity @Table(name = "container") @Inheritance(strategy = InheritanceType.JOINED) public abstract class Container implements Serializable { private String oid; private Long id; @Id

问题 I'm building out a simple eCommerce web app for fun, but for some reason I'm getting an exception with my @OneToOne relationship between a User and a shopping Cart I'm pretty well versed with Hibernate and bi-directional relationships, so I do know that you need to set each relationship in the bi-directional relationship... but it still seems to fail. Here's my User / Cart objects and the Controller code in question: User.class import java.util.HashSet; import java.util.Set; import javax