01-mysql

CREATE TABLE `employees` (
  `id` INT PRIMARY KEY NOT NULL AUTO_INCREMENT,
  `first_name` VARCHAR(50) NOT NULL,
  `last_name` VARCHAR(50) NOT NULL
);

CREATE TABLE `categories` (
  `id` INT PRIMARY KEY NOT NULL AUTO_INCREMENT,
  `name` VARCHAR(50) NOT NULL
);

CREATE TABLE `products` (
  `id` INT PRIMARY KEY NOT NULL AUTO_INCREMENT,
  `name` VARCHAR(50) NOT NULL,
  `category_id` INT NOT NULL
);
INSERT INTO `employees` (`id`, `first_name`, `last_name`) VALUES
('1', 'Test1', 'Test1'),
('2', 'Test2', 'Test2'),
('3', 'Test3', 'Test3');

ALTER TABLE `employees`
ADD COLUMN `middle_name` VARCHAR(45);

ALTER TABLE `products`
ADD CONSTRAINT `category_id`
  FOREIGN KEY (`category_id`)
  REFERENCES `categories` (`id`)
  ON DELETE NO ACTION
  ON UPDATE cascade;

ALTER TABLE `employees`
CHANGE COLUMN `middle_name` `middle_name` VARCHAR(100) NOT NULL ;