one-to-many

问题 I am using laravel 5.1. The scenario is as follows(this is an example. The real scenario is similar to this example) I have 3 models College Student Teacher A college can have many students but a student can belong to only 1 college. A college can have many teachers but a teacher can belong to only 1 college. I want to establish relationships between these tables in laravel. One of the methods for this is to place a college_id foreign key on the Students and Teachers table. But in my case,

问题 This is a very very simple behavior, but I can't find the way to achieve it with doctrine. I'm going to explain it reducing the complexity with only two entities. Having two entites (Author and Book) related like "One Author owns zero or more books" and "One book is owned by zero or one author", I'm trying to unset the relation between an author and one of his books (from the author side), expecting that book.author_id field in database sets as null. The Entities are defined as follow: Author

问题 i have one to many relationship between author and books, one author has many books.. i have domain class like this Author.groovy class Author { String authorName; String authorAddress; String authorCNIC; static hasMany = [books:Book] static constraints = { books(nullable: true) } } Book.groovy class Book { String bookName; String Isbn; static belongsTo = [author:Author] static constraints = { author(nullable: true) } } now when i call this function def deleteauthor() { def id=params.id

问题 This question is in follow up to this post Grails one to many relationship view The example suggested there is not working and throwing following exception at run time null id in blog.omarello.Phone entry (don't flush the Session after an exception occurs). Stacktrace follows: Message: null id in blog.omarello.Phone entry (don't flush the Session after an exception occurs) Line | Method ->> 43 | doCall in blog.omarello.ContactController$_closure4$$ENLORkU6 - - - - - - - - - - - - - - - - - -

问题 This question is in follow up to this post Grails one to many relationship view The example suggested there is not working and throwing following exception at run time null id in blog.omarello.Phone entry (don't flush the Session after an exception occurs). Stacktrace follows: Message: null id in blog.omarello.Phone entry (don't flush the Session after an exception occurs) Line | Method ->> 43 | doCall in blog.omarello.ContactController$_closure4$$ENLORkU6 - - - - - - - - - - - - - - - - - -

问题 I have a simple databasescheme: User, Account. User has 1-to-many relationship with Account. I have generated a ado.net entity data model, and I can create users and accounts, and even link them together. In the database the account.user_id is correctly filled, so theoretically I should be able to acces User.Account.ToList() in C# through entity. However, When I try to acces User.Account.ToList() I get zero results. User user = db.User.First(U => U.id == 1); List<Account> accounts = user

问题 I have 2 tables. One is called Employee, and the other is called Phones, and an employee can have multiple Phones. Employee Class: @Entity @Table(name = "employee") public class Employee { @Id @Column(name = "id", unique = true, nullable = false) @GeneratedValue(strategy = javax.persistence.GenerationType.IDENTITY) private Integer id; @Column(name = "name", unique = true, nullable = false, length = 25) private String name; @OneToMany(mappedBy="owner", fetch= FetchType.EAGER, orphanRemoval

问题 My Core Data model looks like this: article <--->> category Is it even remotely possible to use NSFetchedResultsController to produce a UITableView that looks something like this? Category 1 - Article A - Article B - Article C Category 2 - Article A - Article D - Article E - Article F Category 3 - Article B - Article C Specifically, I'm interested in the (edge?) case where each UITableView section has a unique title (eg, "Category 1", "Category 2"), but the same object can exist in multiple

问题 I'm using JPA over Hibernate in my web-app. Here are two entities (only getters are shown): class Child { private Parent parent; @ManyToOne(optional=false) @JoinColumn(name="parent_id", referencedColumnName="parent_id", nullable=false, updatable=false) public Parent getParent() { return parent; } } class Parent { private Collection<Child> children; @OneToMany(fetch=FetchType.EAGER, mappedBy="parent", cascade={CascadeType.ALL}) public Collection<Child> getChildren() { return children; } } As

问题 Consider two domain classes; Job and Quote. A Job has many Quotes but a Job also has an accepted quote. The accepted quote is nullable and should only be set once a particular Quote has been accepted by a user. I have the relationships mapped as follows (simplified for the purpose of illustration). class Job { String title Quote acceptedQuote } class Quote { Job job BigDecimal quoteAmount } The resultant tables are exactly what I require (at least aesthetically) but the problem arises when I