text: -- create a database called companyDB
  CREATE database companyDB;
  
  USE companyDB;
  -- create a table called department,primary key on id
  CREATE TABLE department(
    id INTEGER AUTO_INCREMENT NOT NULL,
    name VARCHAR(30),
    PRIMARY KEY (id)
  );
  -- create a table called role,primary key on id
  CREATE TABLE role(
    id INTEGER AUTO_INCREMENT NOT NULL,
    title VARCHAR(30),
    salary DECIMAL(10,4),
    department_id INTEGER NOT NULL,
    
    PRIMARY KEY (id)
  );
  -- create a table called employee, primary key on id
  CREATE TABLE employee(
    id INTEGER AUTO_INCREMENT NOT NULL,
    first_name VARCHAR(30),
    last_name VARCHAR(30),
    role_id INTEGER NOT NULL,
    manager_id INTEGER NOT NULL,
    
    PRIMARY KEY (id)
  );
  