Difference between Primary Key & Unique Key
Primary Key
Unique Key
Primary Key can't accept null values.
Unique key can accept only one null value.
By default, Primary key is clustered index and data in the database table is physically organized in the sequence of clustered index.
By default, Unique key is non-clustered index.
We can have only one Primary key in a table.
We can have more than one unique key in a table.
Primary key can be made foreign key into another table.
Unique key can't be made foreign key into another table.
