text: DROP TABLE IF EXISTS tracker;
  
  CREATE DATABASE tracker;
  
  USE tracker;
  
  CREATE TABLE department (
      id INT NOT NULL auto_increment,
      department_name VARCHAR(30) NOT NULL,
      PRIMARY KEY(id)
  );
  CREATE TABLE roles(
      id INT NOT NULL auto_increment,
      title VARCHAR(30) NOT NULL,
      salary DECIMAL(10,2),
      department_id INT,
      PRIMARY KEY(id),
      CONSTRAINT fk_department FOREIGN KEY (department_id) REFERENCES department(id) 
  );
  CREATE TABLE manager(
      id INT NOT NULL auto_increment,
      first_name VARCHAR(30) NOT NULL,
      last_name VARCHAR(30) NOT NULL,
      roles_id INT,
      PRIMARY KEY(id),
      CONSTRAINT fk_roles FOREIGN KEY (roles_id) REFERENCES roles(id)
  );
  CREATE TABLE employee(
      id INT NOT NULL auto_increment,
      first_name VARCHAR(30) NOT NULL,
      last_name VARCHAR(30) NOT NULL,
      roles_id INT,
      manager_id INT,
      PRIMARY KEY (id),
      
      CONSTRAINT fk_manager FOREIGN KEY (manager_id) REFERENCES manager(id) ON DELETE CASCADE,
      CONSTRAINT fk_role FOREIGN KEY (roles_id) REFERENCES roles(id)
      );