By default, primary key creates clustered index on the column and then enforces the uniqueness of the column whereas the unique key, by default creates a non-clustered index.
Primary Key
- By default, creates Clustered index
- Doesn’t allow null
- Table can have only one Primary Key ( Can include multiple columns together )
Unique Key
- By default, creates non clustered index
- Accepts null value
- Table can have many unique keys
