Which concept ensures that each record in a table is unique?

Which concept ensures that each record in a table is unique?

• A. Private Key
• B. Foreign Key
• C. Index
• D. Primary Key

Answer: (D)

Uniquely identifying each row in a table is the job of the primary key. It guarantees that no two rows share the same value for that key and, by default, it cannot be null, so every record has a distinct identity. This unique identifier is what other tables rely on when establishing relationships via foreign keys. A foreign key enforces referential integrity to another table but doesn’t by itself ensure that the rows in the local table are unique. An index improves search speed, but unless it’s defined as unique, it doesn’t guarantee uniqueness of rows. A private key is a cryptography concept and isn’t used to identify records in a database table. So the primary key best ensures that each record is unique.

Uniquely identifying each row in a table is the job of the primary key. It guarantees that no two rows share the same value for that key and, by default, it cannot be null, so every record has a distinct identity. This unique identifier is what other tables rely on when establishing relationships via foreign keys. A foreign key enforces referential integrity to another table but doesn’t by itself ensure that the rows in the local table are unique. An index improves search speed, but unless it’s defined as unique, it doesn’t guarantee uniqueness of rows. A private key is a cryptography concept and isn’t used to identify records in a database table. So the primary key best ensures that each record is unique.