What are the limitations of a Primary Key?

Primary Key Constraints:

1. Uniqueness: Values in the primary key column(s) must be unique for each row in the table.
2. NULL not allowed: Columns declared as primary key cannot contain NULL values.
3. One primary key per table: A table can have only one primary key, but it can consist of multiple columns (composite key).
4. Stability of values: Primary key values should not change frequently, as this can affect data integrity and performance.

These constraints ensure the unique identification of each record in the table and maintain data integrity.