CREATE TABLE employees (  
    employee_id INT PRIMARY KEY AUTO_INCREMENT,  
    last_name VARCHAR(255) NOT NULL,  
    room_number VARCHAR(50),  
    department VARCHAR(255)  
);  

CREATE TABLE computers (  
    computer_id INT PRIMARY KEY AUTO_INCREMENT,  
    model VARCHAR(255) NOT NULL,  
    serial_number VARCHAR(255) UNIQUE,  
    employee_id INT,  
    FOREIGN KEY (employee_id) REFERENCES employees(employee_id) ON DELETE SET NULL  
);
