Understanding the Difference between Primary Key and Unique Key Constraint in Oracle

When it comes to database management in Oracle, it's crucial to grasp the distinction between a primary key and a unique key constraint. Let's delve into the details:

Primary Key Constraint

A primary key is a field (or combination of fields) in a table that uniquely identifies each record in that table. It must have a unique value for each row and cannot contain null values. Only one primary key can be defined for a table, making it a powerful tool for enforcing entity integrity.

Unique Key Constraint

On the other hand, a unique key constraint also ensures data uniqueness but allows for one null value. It guarantees that all values in a column (or a group of columns) are distinct from one another. Unlike a primary key, a table can have multiple unique key constraints defined.

Therefore, the key difference lies in the requirement of null values and the number of key constraints that can be defined in a table. Understanding and properly utilizing primary and unique keys can enhance data integrity and optimize database performance in Oracle.