What is the difference between unique key and primary key?

What is the difference between unique key and primary key?

After clearly reading your question the following is the notable difference between the two items.

·         A unique key although similar to a primary key can contain more than one unique constraint in a given table whereas a primary key cannot

·         A unique key accepts null values whereas a primary key does not

·         A unique key is used for the purpose of preventing duplication of key values within a given row of a table as well as allowance of null values whereas the primary key is used to uniquely identify a given row in a table as well as ensuring that no duplicate rows exist

·         Non-clustered indexes are never created in unique key whereas they are created in primary key