instruction: For those employees who was hired before 2002-06-21, draw a bar chart about the distribution of job_id and the sum of employee_id , and group by attribute job_id, and show bars from high to low order please.
response: SELECT JOB_ID, SUM(EMPLOYEE_ID) FROM employees WHERE HIRE_DATE < '2002-06-21' GROUP BY JOB_ID ORDER BY JOB_ID DESC