Let's first create

note

table without any column to have

AUTO_INCREMENT

CREATE TABLE note (
    id int,
    title varchar(50),
    description varchar(50),
    PRIMARY KEY(id, title)
);

After running the query above, we can add

AUTO_INCREMENT

feature to the existing column

id

ALTER TABLE note MODIFY id int NOT NULL AUTO_INCREMENT;

If the column is not

primary key

initially, we can modify the query, not to cause any error when adding

AUTO_INCREMENT

to it

CREATE TABLE note (
    id int,
    title varchar(50),
    description varchar(50)
);

Adding

AUTO_INCREMENT

feature to the column, that is not selected as a

primary key

ALTER TABLE note MODIFY id int NOT NULL PRIMARY KEY AUTO_INCREMENT