What is diff between unique and primary?

Answer 1

Unique doesn't allows duplicate values but it allows null values.
Primary key is used to uniquely identify the records in the table. and it doesn't allows both duplicate and null values.

Answer 2

Primary key also allows to access data faster

Answer 3

both unique and primary key does not allow duplicate values .
but unique key allows null value but primary key does not allow null value
and also primary key values are arranged in ascending order by default but unique key values are not arranged in ascending order.