object-relationships

How to set a 0..* relationship in Entity Framework Code First?

由 别说谁变了你拦得住时间么 提交于 2020-01-01 04:38:09
问题 I have the next code for two classes: public class Object { public int ObjectID { get; set; } public int Object2ID { get; set; } public virtual Object2 Object2 { get; set; } } public class Object2 { public int Object2ID { get; set; } public virtual ICollection<Object> Objects { get; set; } } I know that with Entity Framework, this will create a one-to-many relationship, but what I want to know, is how to transform this to a zero-to-many relationship. I'm new to Entity Framework and I couldn't

“is A” VS “is Like A” relationships, what does each one mean and how do they differ?

由 巧了我就是萌 提交于 2019-12-21 12:58:16
问题 First an example to discuss: class Foo { // Attributes: int attribute1, attribute2; // Methods: virtual void Foo1() { /* With or without Implementation */ } virtual void Foo2() { /* Also with or without Implementation */ } }; class ExactDuplicate: Foo // No New Attributes or Methods { virtual void Foo1() { /* A new Implementation */ } // Also there might be new Implementations to other methods }; class ExtraMethods: Foo // Having New Methods { virtual void Foo3() { /* Implementation */ } };

JPA - Entity design problem

由 烈酒焚心 提交于 2019-12-17 16:22:52
问题 I am developing a Java Desktop Application and using JPA for persistence. I have a problem mentioned below: I have two entities: Country City Country has the following attribute: CountryName (PK) City has the following attribute: CityName Now as there can be two cities with same name in two different countries, the primaryKey for City table in the datbase is a composite primary key composed of CityName and CountryName . Now my question is How to implement the primary key of the City as an

Retrieving relationships of relationships using Eloquent in Laravel

由 吃可爱长大的小学妹 提交于 2019-11-30 08:09:19
I have a database with the following tables and relationships: Advert 1-1 Car m-1 Model m-1 Brand If I want to retrieve an Advert, I can simply use: Advert::find(1); If I want the details of the car, I could use: Advert::find(1)->with('Car'); However, if I also want the detail of the Model (following the relationship with Car), what would the syntax be, the following doesn't work: Advert::find(1)->with('Car')->with('Model'); Many thanks It's in the official documentation under "Eager Loading" Multiple relationships: $books = Book::with('author', 'publisher')->get(); Nested relationships:

Retrieving relationships of relationships using Eloquent in Laravel

由 允我心安 提交于 2019-11-29 06:01:02
问题 I have a database with the following tables and relationships: Advert 1-1 Car m-1 Model m-1 Brand If I want to retrieve an Advert, I can simply use: Advert::find(1); If I want the details of the car, I could use: Advert::find(1)->with('Car'); However, if I also want the detail of the Model (following the relationship with Car), what would the syntax be, the following doesn't work: Advert::find(1)->with('Car')->with('Model'); Many thanks 回答1: It's in the official documentation under "Eager

JPA - Entity design problem

由 ▼魔方 西西 提交于 2019-11-27 22:28:47
I am developing a Java Desktop Application and using JPA for persistence. I have a problem mentioned below: I have two entities: Country City Country has the following attribute: CountryName (PK) City has the following attribute: CityName Now as there can be two cities with same name in two different countries, the primaryKey for City table in the datbase is a composite primary key composed of CityName and CountryName . Now my question is How to implement the primary key of the City as an Entity in Java @Entity public class Country implements Serializable { private String countryName; @Id
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