What is a primary and unique key?

Question

Accepted Answer

Primary keys uniquely identify records in a database, while unique keys ensure no duplicate values in a column.

A primary key is a unique identifier for a record in a table, e.g., 'CustomerID' in a 'Customers' table.
A table can have only one primary key, but it can consist of multiple columns (composite key).
A unique key also enforces uniqueness but allows for one NULL value, e.g., 'Email' in a 'Users' table.
Primary keys cannot accept NULL values, ensuring every record is identifiable.
Both keys improve data integrity and help in establishing relationships between tables.