Which best describes a Primary Key?

Which best describes a Primary Key?

• A. A date field
• B. A foreign key
• C. A numeric identifier only
• D. A field or combination of fields that uniquely identify a record

Answer: (D)

A primary key is what uniquely identifies each row in a table. It must have unique values for every record and cannot be null, ensuring you can distinguish every entry. Because of that, the primary key can be a single field (often a numeric ID) or a combination of fields if no single field guarantees uniqueness. A date field by itself isn’t guaranteed to be unique, since many records can share the same date. A foreign key, meanwhile, is a separate concept: a field that references the primary key in another table to establish relationships. And a primary key isn’t limited to numbers; it can be non-numeric or composite. So the best description is a field or combination of fields that uniquely identify a record.

A primary key is what uniquely identifies each row in a table. It must have unique values for every record and cannot be null, ensuring you can distinguish every entry. Because of that, the primary key can be a single field (often a numeric ID) or a combination of fields if no single field guarantees uniqueness. A date field by itself isn’t guaranteed to be unique, since many records can share the same date. A foreign key, meanwhile, is a separate concept: a field that references the primary key in another table to establish relationships. And a primary key isn’t limited to numbers; it can be non-numeric or composite. So the best description is a field or combination of fields that uniquely identify a record.