What is the difference between a primary key and a unique key?

Primary key uniquely identifies each record in a table, while unique key ensures each value in a column is unique.

• Primary key does not allow NULL values, while unique key allows one NULL value.

• A table...read more

The primary key does not store null values, whereas the unique key does. A table can only have one primary key, whereas it can have multiple unique keys. The primary key does not allow you to delete o...read more