text: DROP DATABASE IF EXISTS employeeDB;
  CREATE database employeeDB;
  
  USE employeeDB;
  
  
  CREATE TABLE departments (
    id INT NOT NULL AUTO_INCREMENT,
    name VARCHAR(30) NULL,
    PRIMARY KEY (id)
  );
  
  CREATE TABLE roles (
    id INT NOT NULL AUTO_INCREMENT,
    title VARCHAR(30) NULL,
    salary decimal NULL,
    department_id INT NULL,
    PRIMARY KEY (id),
    FOREIGN KEY (department_id) REFERENCES departments(id)
  );
  
  CREATE TABLE employees (
    id INT NOT NULL AUTO_INCREMENT,
    first_name VARCHAR(30) NULL,
    last_name VARCHAR(30) NULL,
    role_id INT NULL,
    manager_id INT NULL,
    PRIMARY KEY (id),
    FOREIGN KEY (role_id) REFERENCES roles(id),
    FOREIGN KEY (manager_id) REFERENCES employees(id)
  );
  
  INSERT INTO departments (name) values ('Physics');
  INSERT INTO departments (name) values ('CS');
  INSERT INTO departments (name) values ('HR');
  
  INSERT INTO roles (title,salary,department_id) values ('Physics Director',250000,1);
  INSERT INTO roles (title,salary,department_id) values ('Physics Professor',200000,1);
  INSERT INTO roles (title,salary,department_id) values ('Physics Associate Professor',150000,1);
  INSERT INTO roles (title,salary,department_id) values ('Physics Assistent Professor',100000,1);
  
  INSERT INTO roles (title,salary,department_id) values ('CS Director',500000,2);
  INSERT INTO roles (title,salary,department_id) values ('CS Professor',400000,2);
  INSERT INTO roles (title,salary,department_id) values ('CS Associate Professor',300000,2);
  INSERT INTO roles (title,salary,department_id) values ('CS Assistent Professor',150000,2);
  
  INSERT INTO roles (title,salary,department_id) values ('HR Director',200000,3);
  INSERT INTO roles (title,salary,department_id) values ('HR Senior Staff',180000,3);
  INSERT INTO roles (title,salary,department_id) values ('HR Staff',120000,3);
  INSERT INTO roles (title,salary,department_id) values ('HR Assistent Staff',80000,3);
  
  
  INSERT INTO employees (first_name,last_name,role_id) values ('Kai','Zhang',1);
  INSERT INTO employees (first_name,last_name,role_id) values ('Zongju','Zhou',9);
  INSERT INTO employees (first_name,last_name,role_id) values ('Ethan','Zhang',5);
  INSERT INTO employees (first_name,last_name,role_id,manager_id) values ('Abigail','Zhang',2,1);
  
  