CREATE TABLE `towns` (
    `id` INT UNSIGNED NOT NULL UNIQUE AUTO_INCREMENT,
    `name` VARCHAR(30) NOT NULL,
    CONSTRAINT `pk_towns` PRIMARY KEY (`id`)
);

CREATE TABLE `addresses` (
    `id` INT UNSIGNED NOT NULL UNIQUE AUTO_INCREMENT,
    `address_text` VARCHAR(30) NOT NULL,
    `town_id` INT UNSIGNED,
    CONSTRAINT `pk_addresses` PRIMARY KEY (`id`),
    CONSTRAINT `fk_addresses_towns` FOREIGN KEY (`town_id`)
        REFERENCES `towns` (`id`)
);

CREATE TABLE `departments` (
    `id` INT UNSIGNED NOT NULL UNIQUE AUTO_INCREMENT,
    `name` VARCHAR(30) NOT NULL,
    CONSTRAINT `pk_departments` PRIMARY KEY (`id`)
);

CREATE TABLE `employees` (
    `id` INT UNSIGNED NOT NULL UNIQUE AUTO_INCREMENT,
    `first_name` VARCHAR(30) NOT NULL,
    `middle_name` VARCHAR(30),
    `last_name` VARCHAR(30) NOT NULL,
    `job_title` VARCHAR(30) NOT NULL,
    `department_id` INT UNSIGNED,
    `hire_date` DATE,
    `salary` DECIMAL(10 , 2 ),
    `address_id` INT UNSIGNED,
    CONSTRAINT `pk_employees` PRIMARY KEY (`id`),
    CONSTRAINT `fk_employees_departments` FOREIGN KEY (`department_id`)
        REFERENCES `departments` (`id`),
    CONSTRAINT `fk_employees_addresses` FOREIGN KEY (`address_id`)
        REFERENCES `addresses` (`id`)
);