What is a foreign key?

technology databases

  1. The foreign key is a column that can have NULL values.

  2. The foreign key is a SQL locking mechanism.

  3. A foreign key is a key field (column) in a database table, which relates the table to another table where the key is a primary key. The primary - foreign key relations are used to cross-reference database tables.

  4. The foreign key is a column that should be primary key for that table.

Show answer
Correct Option: C
Explanation:

To understand what a foreign key is, the user needs to have a basic understanding of database design.

The correct answer is:

C. A foreign key is a key field (column) in a database table, which relates the table to another table where the key is a primary key. The primary-foreign key relations are used to cross-reference database tables.

Explanation of options:

A. This option is incorrect because a foreign key cannot have NULL values. A foreign key must reference a valid primary key in another table.

B. This option is incorrect because a foreign key is not related to SQL locking mechanisms. SQL locking mechanisms are used to manage concurrent access to data.

D. This option is incorrect because a foreign key cannot be a primary key for that table. A primary key is a unique identifier for a table, while a foreign key is used to reference a primary key in another table.

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