Lesson 30: Add Composite Key to Existing Table in PostgreSQL ALTER TABLE Guide
In this lesson, you will learn how to use the ALTER TABLE command in PostgreSQL to add a composite primary key to an existing table.
A composite key is created by combining two or more columns to uniquely identify each row when a single column is not enough. You will see how to define multiple columns together as a primary key and ensure there are no duplicate combinations or NULL values.
By the end of this lesson, you will understand how to apply a composite key step by step and improve data integrity in real-world database scenarios.