What is the difference between primary key and unique key and foreign key in Oracle?
|S.no||Primary Key||Unique Key||Foreign Key|
|1.||Cannot have a NULL value||It can have a NULL value||It can accept the NULL value|
|2.||It is a clustered index||It is a non-clustered index||The Index is manually created whether clustered or non-clustered|
|3.||The Primary key can only be 1 in a table||The Unique key can be more than 1 in a table||The Foreign key can be more than 1 in a table|