Join table

As explained in .NET in Action, Second Edition

A join table is an intermediary database table that stores associations between entities in a many-to-many relationship.

In a many-to-many relationship, EF Core creates a third table to associate the entities. For Books and Tags, that join table has a compound primary key made from both IDs, with foreign keys applied to the join table. The entity classes need no foreign-key ID properties for this relationship. section 5.2.3

Figure 5.4 Many-to-many relationship

View the many-to-many relationship between Book and Tag. section 5.2.3

How .NET in Action, Second Edition covers it

How deep it goes

Explains automatic table creation, the compound primary key, and foreign keys.

Examples

Uses Books and Tags as the entities in a many-to-many relationship.

What you can do after

Understand how EF Core represents a many-to-many association in the database.

How it connects

Connects many-to-many relationships with foreign keys and compound primary keys.

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Also explained in

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  Grokking Relational Database DesignA junction table is a relational table that represents a many-to-many relationship by storing references to the participating entities.
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  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.
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  Building Web APIs with ASP.NET CoreA junction table is a database table that associates rows from two other tables to represent a many-to-many relationship.
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  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.

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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 .NET in Action, Second Edition. The section links point to the parts of the book it draws on.