What is a Primary Key?

What is a Primary Key?

• A. A field (or fields) in a table in which the values entered in the fields are unique, thus ensuring every record in a table is unique.
• B. A key that is usually used to decrypt data.
• C. A foreign key.
• D. An index.

Answer: (A)

A primary key is the field (or combination of fields) that uniquely identifies each row in a table. Its values must be unique and not null, so no two records share the same key and every record can be precisely identified. This unique identifier is what other tables use to relate data through foreign keys, linking related data across the database. In most database systems, the primary key also gets an index to speed up lookups and enforce uniqueness, but the concept centers on identifying records, not on encryption or simple indexing; it’s distinct from a foreign key, which points to a key in another table.

A primary key is the field (or combination of fields) that uniquely identifies each row in a table. Its values must be unique and not null, so no two records share the same key and every record can be precisely identified. This unique identifier is what other tables use to relate data through foreign keys, linking related data across the database. In most database systems, the primary key also gets an index to speed up lookups and enforce uniqueness, but the concept centers on identifying records, not on encryption or simple indexing; it’s distinct from a foreign key, which points to a key in another table.