What is a database primary key?

What is a database primary key?

• A. A generic field that can hold any data
• B. The total number of records in a table
• C. A unique identifier for each row in a table
• D. A foreign key to another table

Answer: (C)

A primary key is a unique identifier for each row in a table. This means every row has a distinct value for the primary key, and that value cannot be null. The primary key uniquely identifies records, and it’s usually indexed to make lookups fast. It also enables relationships with other tables through foreign keys, so data can be linked reliably across the database. The other descriptions miss the core idea: a generic field can hold any data and isn’t guaranteed to be unique; counting how many records exist isn’t identifying specific rows; and a foreign key points to a row in another table rather than identifying the row within the same table.

A primary key is a unique identifier for each row in a table. This means every row has a distinct value for the primary key, and that value cannot be null. The primary key uniquely identifies records, and it’s usually indexed to make lookups fast. It also enables relationships with other tables through foreign keys, so data can be linked reliably across the database.

The other descriptions miss the core idea: a generic field can hold any data and isn’t guaranteed to be unique; counting how many records exist isn’t identifying specific rows; and a foreign key points to a row in another table rather than identifying the row within the same table.