Question

伙计们，我必须选择每个员工，他的薪水比他所在部门的薪水多，有一个代码可以解决这个问题，就在这里

select * from
(select  e.first_name || ' ' || e.last_name ENAME,
d.department_name,e.salary, trunc(e.salary-avg(salary) over (partition by
  e.department_id)) sal_dif
  from employees e,departments d
  where  e.department_id=d.department_id)
  where sal_dif>0

当我运行它时，它工作正常，而且这个代码的成本在我的计算机中是6，我试图用另一种方式来做，像这样

select   first_name || ' '|| last_name,salary
  from
  (select first_name || ' ' || last_name,salary ,avg(salary) over (partition by  department_id) avg_salary
  from employees )
  where salary>avg_salary;

我很惊讶，尽管数据库中存在last_name和first_name，但错误

shows me ORA-00904: "LAST_NAME": invalid identifier
00904. 00000 -  "%s: invalid identifier"
*Cause:    
*Action:
Error at Line: 8 Column: 29

为什么？我可以用其他方式重写第一个代码吗？非常感谢

Answer 1

select name,salary
from
(select first_name || ' ' || last_name as name,salary ,avg(salary) over (partition by     department_id) avg_salary
  from employees )
  where salary>avg_salary;

Answer 2

使用别名来标识列：

select   full_name,salary
  from
  (select first_name || ' ' || last_name as full_name,salary ,avg(salary) over (partition by  department_id) avg_salary
  from employees )
  where salary>avg_salary;

Answer 3

作为在子查询中对组合列进行别名的替代方法，不要将子查询中的列组合在一起 - 而是将连接替换为,，如下所示：

select   first_name || ' '|| last_name,salary
from
  (select first_name, last_name, salary,
          avg(salary) over (partition by  department_id) avg_salary
   from employees)
where salary>avg_salary;

优化sql代码

3 个答案: