Join table

As explained in Building Web APIs with ASP.NET Core

A junction table is a database table that associates rows from two other tables to represent a many-to-many relationship.

A join table is a database table that connects rows from two other tables, representing a many-to-many relationship. Instead of storing every relationship inside either related table, the relationship gets its own table. section 4.1.1

In the board-game schema, the BoardGames table connects to Domains and Mechanics through the BoardGames_Domains and BoardGames_Mechanics join tables. These tables support relationships such as a game having multiple domains or mechanics. section 4.2.4 section 4.1.1

Join tables affect the design and retrieval of relational data in several ways:

• Require additional tables when the model contains more many-to-many relationships. section 4.1.1
• Increase the number of JOINs needed to retrieve related information. section 4.1.1
• Contrast with a document-oriented design, where related mechanics and domains can be embedded in a boardGames collection. section 4.1.1

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

Use the relational schema diagram to trace how BoardGames connects to Domains and Mechanics through separate join tables. section 4.1.1

How Building Web APIs with ASP.NET Core covers it

How deep it goes

Defines the schema role and retrieval cost, but does not provide join-table SQL or CRUD implementation.

Examples

Uses BoardGames_Domains and BoardGames_Mechanics in a board-game database schema.

What you can do after

Evaluate relational and document-oriented schema choices involving many-to-many data.

How it connects

Connects relational tables, many-to-many relationships, JOINs, and embedded collections.

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Also explained in

• 

  liveBookmanning.com
  Grokking Relational Database DesignA junction table is a relational table that represents a many-to-many relationship by storing references to the participating entities.
• 

  liveBookmanning.com
  Java Persistence with Spring Data and Hibernate epubA join table is a relational table that stores key-based links between rows of associated entity tables, commonly for a many-to-many association.
• 

  liveBookmanning.com
  The Well-Grounded Python Developer: How the pros use Python and FlaskAn association table is a relational table that records associations between entities from two other tables, typically through foreign keys.
• 

  liveBookmanning.com
  .NET in Action, Second EditionA join table is an intermediary database table that stores associations between entities in a many-to-many relationship.

Compare how 5 books explain join table →

Related concepts

• many-to-many relationshipused by · A many-to-many relationship is an association in which multiple instances of each participating entity can relate to multiple instances of the other.
• Entity Framework Coreproduced by · Entity Framework Core is a cross-platform object-relational mapping framework for .NET that enables applications to query and persist data through .NET objects and APIs.
• dependent entitykind of · A dependent entity is an entity whose identification or existence depends on a related owner entity and cannot be fully determined independently.
• one-to-one relationshipused by · A one-to-one relationship is an association in which each instance of either entity type relates to at most one instance of the other type.

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.