What is a primary key in a relational database?

What is a primary key in a relational database?

• A. Foreign Key
• B. Composite Index
• C. Primary Key
• D. Many-to-Many Relationship

Answer: (C)

A primary key is the unique identifier for each row in a table. It must be unique and not null, so every record can be precisely located and referenced. This key serves as the anchor for relationships, since other tables can reference it with foreign keys to establish links between tables. That’s why the option named as the primary key fits best: it defines what uniquely identifies a record and supports relational integrity. A foreign key points to a primary key in another table, a composite index is about fast lookups, and a many-to-many relationship describes how two tables relate—none of these define the row’s own identity the way a primary key does.

A primary key is the unique identifier for each row in a table. It must be unique and not null, so every record can be precisely located and referenced. This key serves as the anchor for relationships, since other tables can reference it with foreign keys to establish links between tables.

That’s why the option named as the primary key fits best: it defines what uniquely identifies a record and supports relational integrity. A foreign key points to a primary key in another table, a composite index is about fast lookups, and a many-to-many relationship describes how two tables relate—none of these define the row’s own identity the way a primary key does.