oracle数据库：基本查询、层次查询和level伪列查询

1、查询每个部门、职位的总工资，以及每个部门的总工资，整个公司的总工资。

select department_id,job_id,sum(salary)
	from employees
	group by rollup(department_id,job_id);

2、查询每个部门、职位的总工资，以及每个部门的总工资，整个公司的总工资。

select department_id,job_id,sum(salary)
	from employees
	group by cube(department_id,job_id);

3、使用grouping函数，在合适的地方写上部门小计，职位小计和总计。

select
    case grouping(department_id)
    when 1 then 'all department'
    else to_char(department_id)
    end as department,
    case grouping(job_id)
    when 1 then 'all jobs'
    else job_id
    end as job,
    sum(salary)
    from employees
    group by rollup(department_id,job_id)
order by department_id,job_id;

4、使用层次查询和level伪列查询公司管理层次图。

select level,employee_id,manager_id,last_name,job_id from employees
	start with job_id = (select job_id from employees where employee_id=108)
	connect by prior manager_id=employee_id;

5、使用层次查询和level伪列查询某个领导的直接和间接员工。

select level,employee_id,manager_id,last_name,job_id from employees
      start with job_id=(select job_id from employees where employee_id=108)
      connect by prior employee_id=manager_id;