What are the main criteria for choosing a primary key in a database?

Main criteria for choosing a primary key in a database:

• Uniqueness: The key value must uniquely identify each record.
• Immutability: The primary key value should not change over time.
• Minimal size: It is better to choose a key with the smallest size for index optimization and performance.
• Simplicity: The key should be simple to understand and use.
• No NULLs: The primary key cannot contain NULL values.

Example: often auto-incrementing integer fields or UUIDs are used when global uniqueness is required.