text: --1. List the following details of each employee: employee number, last name, first name, sex, and salary.
  SELECT employees.emp_no, 
  employees.last_name, 
  employees.first_name, 
  employees.sex, 
  salaries.salary
  FROM employees
  LEFT JOIN salaries
  ON employees.emp_no = salaries.emp_no
  ORDER BY emp_no
  
  --2. List first name, last name, and hire date for employees who were hired in 1986.
  SELECT * FROM employees
  WHERE DATE_PART('year', hire_date) = 1986
  ORDER BY emp_no;
  
  --3. List the manager of each department with the following information: department number, department name, the manager's employee number, last name, first name.
  SELECT dept_manager.dept_no, 
  departments.dept_name,
  dept_manager.emp_no,
  employees.last_name, 
  employees.first_name
  FROM dept_manager
  LEFT JOIN departments
  ON dept_manager.dept_no = departments.dept_no
  LEFT JOIN employees 
  ON dept_manager.emp_no = employees.emp_no
  ORDER BY emp_no
  
  --4. List the department of each employee with the following information: employee number, last name, first name, and department name.
  SELECT employees.emp_no,
  employees.last_name,
  employees.first_name,
  dept_emp.dept_no,
  departments.dept_name
  FROM employees 
  INNER JOIN dept_emp ON employees.emp_no=dept_emp.emp_no
  INNER JOIN departments ON departments.dept_no=dept_emp.dept_no
  ORDER BY emp_no;
  
  --5. List first name, last name, and sex for employees whose first name is "Hercules" and last names begin with "B."
  SELECT * FROM employees
  WHERE first_name = 'Hercules' AND last_name like 'B%';
  
  --6. List all employees in the Sales department, including their employee number, last name, first name, and department name.
  SELECT 
  employees.emp_no, 
  employees.last_name, 
  employees.first_name,
  dept_emp.dept_no
  FROM employees 
  LEFT JOIN dept_emp 
  ON employees.emp_no=dept_emp.emp_no
  INNER JOIN departments 
  ON departments.dept_no=dept_emp.dept_no
  WHERE departments.dept_name='Sales';
  
  --7. List all employees in the Sales and Development departments, including their employee number, last name, first name, and department name.
  SELECT 
  employees.emp_no, 
  employees.last_name, 
  employees.first_name,
  dept_emp.dept_no
  FROM employees 
  LEFT JOIN dept_emp 
  ON employees.emp_no=dept_emp.emp_no
  INNER JOIN departments 
  ON departments.dept_no=dept_emp.dept_no
  WHERE departments.dept_name in ('Sales', 'Development')
  
  --8. In descending order, list the frequency count of employee last names, i.e., how many employees share each last name.
  SELECT last_name, COUNT(*) AS freq_count
  FROM employees
  GROUP BY last_name
  ORDER BY freq_count DESC;