Google Data Analytics Professional Certification Practice Test

What is the function of a foreign key in a table?

1. An identifier for the table

2. A field that references a primary key in another table

3. A method for data encryption

4. A unique identifier for each record

The correct answer is: A field that references a primary key in another table

A foreign key serves a critical role in relational databases by establishing a link between two tables. Specifically, it is a field (or collection of fields) in one table that uniquely identifies a row in another table, typically referencing the primary key of that other table. This relationship is vital for maintaining data integrity and enforcing referential integrity within the database. When a foreign key relationship is created, it allows for the establishment of connections between records in different tables, facilitating complex queries and joins that can pull relevant data from multiple sources. This structure supports the normalization process, which helps to eliminate redundancy and enhance data organization by segregating different pieces of data into related tables. In contrast, the other options do not accurately describe the function of a foreign key: - An identifier for the table does not encapsulate the specific role of a foreign key, as this function is typically fulfilled by primary keys. - A method for data encryption is unrelated to the relational database's structure and data relationships. - A unique identifier for each record generally refers to a primary key rather than a foreign key. Consequently, understanding the role of a foreign key is essential for anyone working within a relational database as it impacts how data is related and retrieved efficiently.