What is polymorphic Association SQL?

What is polymorphic Association SQL?

The indications that the Requirements create a situation where someone might try to use a Polymorphic Association are: There are several entities which are sufficiently similar that you consider having one entity, but are sufficiently different that you think multiple entities are justified.

What is polymorphic association in Rails?

In Ruby on Rails, a polymorphic association is an Active Record association that can connect a model to multiple other models. For example, we can use a single association to connect the Review model with the Event and Restaurant models, allowing us to connect a review with either an event or a restaurant.

What is polymorphic association in Sequelize?

A polymorphic association consists on two (or more) associations happening with the same foreign key. For example, consider the models Image , Video and Comment . The first two represent something that a user might post. We want to allow comments to be placed in both of them.

What is a polymorphic key?

A polymorphic key is an ID that can refer to more than one type of object as a parent. For example, either a Contact or a Lead can be the parent of a task. In other words, the WhoId field of a task can contain the ID of either a Contact or a Lead.

What is polymorphic relationship laravel?

A one-to-one polymorphic relationship is a situation where one model can belong to more than one type of model but on only one association. A typical example of this is featured images on a post and an avatar for a user. The only thing that changes however is how we get the associated model by using morphOne instead.

Has one vs belong to?

They essentially do the same thing, the only difference is what side of the relationship you are on. If a User has a Profile , then in the User class you’d have has_one :profile and in the Profile class you’d have belongs_to :user .

What is dependent destroy in rails?

You do that by setting dependent: :destroy on the has_many relationship. Like so: class Parent ApplicationRecord has_many :children, dependent: :destroy end. Rails, when attempting to destroy an instance of the Parent, will also iteratively go through each child of the parent calling destroy on the child.

What is polymorphic database?

Polymorphic association is a term used in discussions of Object-Relational Mapping with respect to the problem of representing in the relational database domain, a relationship from one class to multiple classes. In statically typed languages such as Java these multiple classes are subclasses of the same superclass.

What are two types of polymorphism?

Types of Polymorphism

  • Subtype polymorphism (Runtime) Subtype polymorphism is the most common kind of polymorphism.
  • Parametric polymorphism (Overloading)
  • Ad hoc polymorphism (Compile-time)
  • Coercion polymorphism (Casting)

What is polymorphism and types of polymorphism?

Polymorphism is the ability to process objects differently on the basis of their class and data types. There are two types of polymorphism in Java: compile time polymorphism and run time polymorphism in java. This java polymorphism is also referred to as static polymorphisms and dynamic polymorphisms.

What is belongsTo in Laravel?

BelongsTo relationship in laravel is used to create the relation between two tables. belongsTo means create the relation one to one in inverse direction or its opposite of hasOne. For example if a user has a profile and we wanted to get profile with the user details then we can use belongsTo relationship.

What is difference between belongsTo and hasOne?

The only difference between hasOne and belongsTo is where the foreign key column is located. Let’s say you have two entities: User and an Account. In short hasOne and belongsTo are inverses of one another – if one record belongTo the other, the other hasOne of the first.