Adding Columns to Tables in PostgreSQL

Suppose we have a table named employees with these columns:

To add new columns, use the syntax:

ALTER TABLE employees
ADD COLUMN column_name data_type [constraints];

Important: The ALTER TABLE ... ADD COLUMN command does not produce output. It only modifies the table structure.

Example 1: Add a phone number column

ALTER TABLE employees
ADD COLUMN phone VARCHAR(15);

After this, the employees table will look like:

Example 2: Add a status column with constraints and default

ALTER TABLE employees
ADD COLUMN status VARCHAR(20) NOT NULL DEFAULT 'active';

After this, the employees table will look like: