Consider the following statements :

I - The primary key of a relation cannot contain null values.

II - Unique Key can have null values.

Which among the following is true ? 

The correct answer is Both I and II are true.

Key Points

• The primary key of a relation cannot contain null values. This is because the primary key uniquely identifies each record in a database table, and having a null value would violate this uniqueness constraint.
• A unique key can have null values. While unique keys ensure that all values in a column are different, they do allow for null values, as nulls are not considered equal to any other value, including other nulls.

Additional Information

• Primary keys are used to establish and enforce entity integrity, ensuring that each record in a table is unique and identifiable.
• Unique keys help in ensuring the uniqueness of the column values but can be used in scenarios where null values are permissible.
• Both primary keys and unique keys can be used to enforce constraints and indexes, improving the performance of database queries.
• In a relational database, both primary and unique keys are crucial for maintaining data integrity and efficient data retrieval.