摘要：
-- case的使用 select last_name, department_id, salary, case department_id when 10 then salary * 1.1 when 20 then salary * 1.2 when 30 then salary * 1.3 e 阅读全文
摘要：
select EMPLOYEE_ID, LAST_NAME, SALARY, GRADE_LEVEL from EMPLOYEES e, JOB_GRADES j where e.SALARY between j.LOWEST_SAL and j.HIGHEST_SAL; select last_n 阅读全文