Consider the following statements about keys in a relational database:
I. A primary key is a minimal super key that uniquely identifies each record in a table.
II. A super key is a set of one or more columns that can uniquely identify a record in a table.
III. A foreign key is a set of columns that creates a link between two tables, ensuring referential integrity.
Which of the following options correctly identifies the statements about primary keys, super keys, and foreign keys?

Correct option is D

All three statements are correct:
· Statement I: A primary key is indeed a minimal super key, meaning it is the smallest subset of attributes that can uniquely identify a record.
· Statement II: A super key is any set of one or more columns that uniquely identifies a record, including the primary key and additional attributes.
· Statement III: A foreign key establishes a link between two tables by referring to the primary key of another table, ensuring referential integrity.
Important Key Points:
1. Primary Key: A unique identifier for each record in a table. It cannot contain null values and is a subset of a super key.
2. Super Key: Includes one or more attributes that uniquely identify a record. A primary key is a specific type of super key.
3. Foreign Key: Links two tables by referring to the primary key in the related table, ensuring data consistency.
Knowledge Booster:
· Primary Key vs. Unique Key: Both ensure uniqueness, but a primary key does not allow null values, while a unique key can.
· Composite Key: A primary key that consists of two or more columns.
· Referential Integrity: Enforced by foreign keys to ensure valid and consistent relationships between tables.