Cascade

问题 I have a very simple unidirectional class mappings. public class MyDbContext : DbContext { public MyDbContext() : base("CodeFirstDatabase") { } public DbSet<Contact> Contacts { get; set; } public DbSet<PhoneNumber> Number { get; set; } protected override void OnModelCreating(DbModelBuilder modelBuilder) { modelBuilder.Conventions.Remove<PluralizingTableNameConvention>(); modelBuilder.Conventions.Remove<IncludeMetadataConvention>(); modelBuilder.Entity<Contact>() .HasMany(c => c.Numbers)

问题 class Owner { static hasMany = Dog } class Sitter { static hasMany = Dog } class Dog { static belongsTo = [Owner, Sitter] } My question is: If I create a Dog instance D, a Owner instance O, a Sitter instance S and associate D with both O and S, what happens to O when S gets deleted? Would O still have D? Since it's a cascade-delete, both S and D would get deleted, right? When what happens to O? Would it still have D? 回答1: I have tested it, it follows the cascade rule: if you delete Owner, Dog

问题 I created table with FOREIGN KEY and can't insert anything. CREATE TABLE menus ( id int(10), parent_id int(10), label varchar(255), PRIMARY KEY (id), FOREIGN KEY (parent_id) REFERENCES menus (id) ); I need FOREIGN KEY to automatically delete children when parent was deleted. This table was successfully created but I can't insert anything. INSERT INTO `menus` (`parent_id`, `label`) VALUES ('1', 'label1'); or INSERT INTO `menus` (`label`) VALUES ( 'label1'); #1452 - Cannot add or update a child

问题 I have a set hibernate.hbm2ddl.auto to create so that Hibernate creates the tables in mysql for me. However, it doesn't seem that hibernate correctly adds Cascade on the references in the table. It does however work when I for instance delete a row, and I have a delete cascade as hibernate annotation . So I guess that means that Hibernate reads the annoation on runtime, and perform cascading manually? Is that normal behavior? For instance: @Entity class Report { @OneToOne(cascade =

问题 I have a bit of problems with PreUpdate HasLifecycleCallbacks. I have an entity, let say "A" with have a OneToOne relation with the entity "B". So I have: /** * @ORM\Entity() * @ORM\HasLifecycleCallbacks */ class A { /** * @ORM\OneToOne(targetEntity="B", inversedBy="attrA", cascade={"persist", "remove"}) * @ORM\JoinColumn(name="fieldB", referencedColumnName="id") */ private $attrB; public function __construct() { $this->attrB = new B(); } /** * @ORM\PrePersist * @ORM\PreUpdate */ public

问题 I have a basic one to many relation parent / child like in the chapter 21 of Hibernate references book. The cascade is only from child to parent (persist cascade only because I don't want to delete the parent if I delete a child). When I add a child to the parent and I save the child, I have a TransientObjectException... @Entity public class Parent implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @OneToMany(mappedBy = "parent", orphanRemoval =

问题 I just want to check really quickly. Say I have two entities in a data model: Catalog, and Product. They have a many-to-many relationship with each other, and both are required (a Catalog must have at least one Product, and all Products must each belong to at least one Catalog). So if I was to delete a Product, its deletion should be Nullify, of course. But what should the deletion policy be for Catalog? If a Catalog is deleted, not all of its Products necessarily exclusively belong to it. A

问题 I have the following example: Table A -some_id Table B -another_id Table C -some_id_fk -another_id_fk I want to cascade a row on Table C if both some_id and another_id are deleted from their respective tables. How can I make a row in Table C cascade itself when two foreign keys are deleted? If only one of the FKs is deleted, the affected row should change to a null value in the column referencing that foreign key. 回答1: I suggest two foreign key constraints with ON DELETE SET NULL and a

问题 How can I add a third drop down to this code. I have not been able to figure it out. Thanks!!! <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <script type="text/javascript" src="jqueryui/js/jquery-ui-1.8.15.custom.min.js"></script> <script type="text/javascript" src="jqueryui/js/jquery-1.6.2.min.js"></script> <script type="text/javascript"> $(document).ready(function(){ $("select#category").change(function(){ var id = $(

问题 I cannot cascade merge with persist three levels of entities using @EmbeddedId in the last entity. I have three following entities: 1. Voucher 2. Rate 3. RatePerChannelOverwrite The Voucher is fetched by a service. Then I want to add new Rate to the voucher. Then I want to add new RatePerChannelOverwrite to the Rate . So both Rate and RatePerChannelOverwrite will have their @Id as NULL. This is working. However later I tried to split RatePerChannelOverwrite into two classes and have: