What is a foreign key?

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What is a foreign key?

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A foreign key is the primary key of one entity that is copied into another entity. The objective of a foreign key is to provide a relationship between the two entities. The example given below describes a foreign key. For example, there are two tables, Author and Book.

Author AuthorID Name Contact No. Address

Book BookID Title Category AuthorID

Here, AuthorID is the primary key of the Author table, and it is migrated from the Author table to the Book table. In the Book table, it is referred to as the foreign key.

Note: Here, in the above example, AuthorID becomes the foreign key in the Book table.

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