many-to-many

问题 I have the following data model and i want to break the many-to-many relationship between EntityA and EntityB. I'm doing this by removing EntityC object that connects both of them. I found that EntityA still have a relationship with EntityB although I saved the managed object context, I can see the changes take affect after EntityA records are re-fetched from database. Is there something I'm missing? Thanks in advance,Sarah 回答1: I agree with the comment from Barry, from your description it

问题 I need some help with a problem. I am working on a microsoft database with SQL and I have a Table that looks similar to this one: |*Name*|*Permissions*| |App1 |Permission 1 | |App1 |Permission 2 | |App1 |Permission 3 | |App2 |Permission 1 | |App2 |Permission 2 | |App2 |Permission 3 | So it is an m to n relation ship, as there are multiple permissions assigned to an app but there are also multiple apps using the same permission. I have already tried something like joining the table with itself

问题 I want to render a filtered collection as a checkbox list. But i have trouble to get the collection shown. i get "Catchable Fatal Error: Object of class Doctrine\ORM\PersistentCollection could not be converted to string". Below is my formtype: class PropertyfilterType extends AbstractType { public function buildForm(FormBuilderInterface $builder, array $options) { $builder ->add('view', EntityType::class, [ 'class' => Propsearch::class, 'choice_label' => 'propsearchviews', 'expanded' => true,

问题 I would like to have a queriable collection in my entity that does not persist. In other words, a transient ManytoMany relationship. I have tried: @Transient @ManyToMany(fetch = FetchType.EAGER) @JoinTable(name="QuestionSetClass_Link", schema = "SVY", joinColumns={@JoinColumn(name="QuestionSetID", referencedColumnName="QuestionSetID")}, inverseJoinColumns={@JoinColumn(name="QuestionSetClassID", referencedColumnName="ID")}) private Collection<QuestionSetClass> questionSetClasses; public

问题 I've already searched for my problem, but most of the examples (if not all), have to deal with only one or two tables with a one-to-many relationship between them. So, here goes my scenario: My first table is: OrderID Quantity Price ---------------------------------- 18 1000.00 160.00 19 1000.00 40.00 22 1000.00 40.00 23 100.00 500.00 24 10.00 50.00 My second table is: ExtrasID Name ------------------- 1 Value 1 2 Value 2 3 Value 3 4 Value 4 5 Value 5 I have a many-to-many relationship

问题 I'm in the midst of creating an alarm/notification system for a small Sales CRM app. I have a Lead_Contact model that is used to store a client's name, address, etc. as well as a Contact_Notifier models that is being used to keep track of when a client was first contacted, the last contact, and when we are going to next contact them. For reference, here is the relevant snippets of the models: class Lead_Contact(models.Model): first_contacted = models.ManyToManyField('Contact_Notifier',

问题 I want to read several Elements for a user using Hibernate. These are my tables in the database: And this is the code of my user class: @Entity @Table(name="users") public class User { @Id @GeneratedValue @Column(name="user_id") private int id; @ManyToMany(fetch=FetchType.EAGER, cascade = CascadeType.ALL) @JoinTable(name="mapping", joinColumns=@JoinColumn(name="user_id"), inverseJoinColumns=@JoinColumn(name="element_id") ) private Set<Element> elements; It is an unidirectional mapping. So

问题 I'm having an m:n relationsship like here, except for that there's some information be to associated with the AuthorBook entity. So I guess, I need no @JoinTable at all and should create a class AuthorBook consisting of one link to each of Author and Book and the additional information, right? I tried it like @Entity public class AuthorBook { @Id @ManyToOne Author author; @Id @ManyToOne Book book; @LobOrWhatever AdditionalInformation additionalInformation; } and I ran into problems (I can't

问题 I have a "partial" working code with many to many relationship between Teams and Players (and junction table TeamPlayers). The drop down menu on Team and Player side does not work.Though data is stored in db (Player and Team tables)BUT NOT to junction table TeamPlayers. I want to have the possibility in my view for current players and current teams to be connected, aka, save a current TeamId to TeamId in my junction table (and PlayerId to PlayerId). The last insert step is....i´m totally

问题 I use PostgreSQL10 and I want to built queries that have multiple optional parameters. A user must input area name, but then it is optional to pick none or any combination of the following event, event date, category, category date, style So a full query could be "all the banks (category), constructed in 1990 (category date) with modern architecture (style), that got renovated in 1992 (event and event date) in the area of NYC (area) ". My problem is that all those are in different tables,