2.10f

Understanding Foreign Keys in Databases

Definition of Foreign Key

• A foreign key is a column or a group of columns in a table that refers to the primary key in another table.

• Multiple foreign keys can refer to the same table, establishing relationships among different tables.

Creating a Foreign Key

• To implement a foreign key in a database, it must be defined in the CREATE TABLE statement.

• The syntax for adding a foreign key includes several key components:

  • FOREIGN KEY keyword: Indicates that the column is a foreign key.

  • The name of the foreign key column(s): Specifies which column(s) are referenced.

  • REFERENCES keyword: Indicates the table and column(s) to which the foreign key points.

  • Name of the referenced table: The table that contains the primary key.

  • Name of the referenced primary key column: The specific column in the referenced table that the foreign key corresponds to.