Lesson 29: Add Primary Key Constraint 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 Primary Key constraint to an existing table.
A Primary Key is used to uniquely identify each row in a table, so no duplicate or NULL values are allowed. You will see how to apply a primary key to a column after the table is already created, and what conditions must be met before adding it (like no duplicate values).
By the end of this lesson, you will understand how to enforce uniqueness and improve data integrity by adding a Primary Key to an existing table in a simple and practical way.