Example
CREATE DATABASE stackoverflow;
USE stackoverflow;
Create table stack(
id_user int NOT NULL,
username varchar(30) NOT NULL,
password varchar(30) NOT NULL
);
ALTER TABLE stack ADD COLUMN submit date NOT NULL; -- add new column
ALTER TABLE stack DROP COLUMN submit; -- drop column
ALTER TABLE stack MODIFY submit DATETIME NOT NULL; -- modify type column
ALTER TABLE stack CHANGE submit submit_date DATETIME NOT NULL; -- change type and name of column
ALTER TABLE stack ADD COLUMN mod_id INT NOT NULL AFTER id_user; -- add new column after existing column
