Dear aspirant,

These are some differences:-

Primary key: 1.   A primary key is a column of table which uniquely identifies each tuple (row) in that table.

2.    Primary key enforces integrity constraints to the table.

3.   Only one primary key is allowed to use in a table.

4.   The primary key does not accept the any duplicate and NULL values.

Unique key: 1. Unique key constraints also identifies an individual tuple uniquely in a relation or table.

2.  A table can have more than one unique key unlike primary key.

3. Unique key constraints can accept only one NULL value for column.

4. Unique constraints are also referenced by the foreign key of another table.

*I hope this information helps you.