Many-to-many relationship

As explained in Building Web APIs with ASP.NET Core

A many-to-many relationship is a data-model relationship in which multiple instances of each of two entity types can be associated with multiple instances of the other.

A many-to-many relationship connects multiple instances of one entity type to multiple instances of another. In a relational SQL schema, a junction table records those associations. section 4.4.3 section 4.1.1

Implement the relationship by:

• Creating the two related entities and their database tables. section 4.4.3
• Adding a junction entity with the minimum required properties. section 4.4.3
• Defining navigation properties, foreign keys, cascading rules, and DbSets in the application database context through the Fluent API. section 4.4.3

Board games and categories

A BoardGame can belong to one or more categories, while each Category can describe multiple board games. The Categories table and BoardGames_Categories junction table represent that relationship. section 4.4.3

Figure 4.1 MyBGList database schema diagram for a table-oriented SQL database

Use the relational schema diagram to inspect the main tables, related tables, and junction-table links in the board-game data model. section 4.1.1

How Building Web APIs with ASP.NET Core covers it

How deep it goes

Defines junction entities and descends into navigation properties, foreign keys, cascading rules, DbSets, and Fluent API configuration.

Examples

Uses BoardGame–Domain, BoardGame–Mechanic, and BoardGame–Category associations represented through junction tables.

What you can do after

Build it from scratch by defining related entities, a junction entity, and database-context relationship configuration.

How it connects

Connects SQL databases with relational schemas, junction tables, foreign keys, navigation properties, Fluent API, and JOINs.

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Related concepts

• join tableuses · A join table is a relational database table whose rows store key-based associations between records in two other tables, commonly representing a many-to-many relationship.
• edgekind of · An edge is a graph connection between two vertices that represents a relationship and may be directed, labeled, or weighted.
• entity-relationship diagramused by · An entity-relationship diagram is a visual model representing data entities, their attributes, relationships, and applicable constraints.
• association resourceaddressed by · An association resource is an API resource that represents a relationship between specific resources and whose associated endpoints are fixed for the resource's lifetime.
• custom methodaddressed by · A custom method is a user-defined operation or capability added to an interface to provide behavior beyond its predefined functionality.
• associationkind of · An association is a relationship between model elements, such as classes, whose instances are connected or can interact.

This explainer was generated by Manning's knowledge graph from the text of Building Web APIs with ASP.NET Core. The section links point to the parts of the book it draws on.