显示员工“杰克”被雇用后雇用的员工的详细信息

Question

以下是显示员工“杰克”被聘用后雇用的员工详细信息的代码

所有信息都在一张表中。

我的查询：

select e.employee_name, e.hiredate
from employees e 
where e.employee_hiredate > jack.hiredate;

Answer 1

要获得“杰克”表，您只需要加入：

select e.employee_name, e.hiredate 
from employees e
join employees jack on jack.employee_name = 'Jack'
where e.employee_hiredate > jack.hiredate;

或者，您可以使用子查询：

select e.employee_name, e.hiredate 
from employees e
where e.employee_hiredate > (select hiredate from employees where employee_name = 'Jack');

This article可以为你提供关于联接如何工作的更好解释，this article将解释一些有关子查询的内容。

Answer 2

Select * 
from   employees e 
where  convert(date,e.employee_hiredate)  > (select convert(date,e.employee_hiredate) 
                                             from employees 
                                             where employee = 'jack'
                                            )

Answer 3

由于您要选择仅与特定员工进行比较的记录，因此您可以使用子查询。

在Oracle中，您可以执行以下操作：

select e.employee_name, e.hiredate
from employees e 
where TRUNC(e.employee_hiredate) > (SELECT TRUNC(HIREDATE) FROM EMPLOYEES WHERE EMPLOYEE_NAME = 'Jack');