04-mysql

CREATE TABLE `users` (
  `id` INT PRIMARY KEY NOT NULL AUTO_INCREMENT,
  `username` VARCHAR(30) NULL,
  `password` VARCHAR(26) NULL,
  `profile_picture` BLOB NULL,
  `last_login_time` TIME NULL,
  `is_deleted` TINYINT NULL
);

INSERT INTO `users` (`id`, `username`, `password`, `last_login_time`, `is_deleted`)
VALUES
('1', 'user', 'proba123', '12:30', '0'),
('2', 'user', 'proba123', '12:30', '0'),
('3', 'user', 'proba123', '12:30', '0'),
('4', 'user', 'proba123', '12:30', '0'),
('5', 'user', 'proba123', '12:30', '0');

ALTER TABLE `users`
DROP PRIMARY KEY,
ADD PRIMARY KEY (`id`, `username`);

ALTER TABLE `users`
CHANGE COLUMN `last_login_time` `last_login_time` TIME NOT NULL ;

ALTER TABLE `users`
CHANGE COLUMN `last_login_time` `last_login_time` TIME NOT NULL ,
DROP PRIMARY KEY,
ADD PRIMARY KEY (`id`),
ADD UNIQUE INDEX `username_UNIQUE` (`username` ASC) VISIBLE;