Another major difference is that, primary key doesn't allow NULLs, but unique key allows one NULL.
- Primary key used to uniqly identify each row in Table.
- Primary key does not allow duplicate values and Null values.
- Primary key is default Clustered Indexes
- One table can have only one Primary key.
- Unique Key is used to uniqly identify each row in Table.
- Unique Key does not allow duplicate values but allowes only one Null value.
- Unique Key is default Non- Clustered Indexe
- One table can have more than one Unique Keys.