Primary key uniqueness in DBMS – UGC NET Question

The primary key is chosen to uniquely distinguish each row in a table, ensuring that no two records share the same key value. It enforces entity integrity and is often used in relationships with other tables through foreign keys. Database management systems can index primary keys to speed up data retrieval. Consequently, the key described is the primary key.

Option A:
Option A, alternate, key is a candidate key not chosen as the primary identifier, so while it may also be unique, it is not the designated main key in the table.

Option B:
Option B, foreign, key refers to a field that links to a primary key in another table and does not uniquely identify records within its own table.

Option C:
Option C is correct because data modelling theory and DBMS textbooks clearly define the primary key as the unique identifier that cannot be null or duplicated.

Option D:
Option D, composite, key consists of two or more fields that together uniquely identify a record, but the stem does not imply multiple fields being used.