Default

CREATE TABLE customer
(
    customer_id serial,
    full_name text,
    status char DEFAULT 'r',
    
    CONSTRAINT PK_customer_customer_id PRIMARY KEY(customer_id),
    CONSTRAINT CHK_customer_status CHECK (status = 'r' or status = 'p')
);

INSERT INTO customer (full_name)
VALUES
('name');

SELECT * FROM customer;

-- Drop default
ALTER TABLE customer
ALTER COLUMN status DROP DEFAULT

-- Set default
ALTER TABLE customer
ALTER COLUMN status SET DEFAULT 'r'