[打卡]龙一帆，多变查询③

SELECT e.employee_id,d.department_name

from employees e,departments d

where e.department_id=d.department_id

SELECT employee_id,department_name

from employees e join departments d

on e.department_id=d.department_id

     #inner 内部

SELECT employee_id,department_name

from employees e inner join departments d

on e.department_id=d.department_id

   #加city 99内连接

SELECT employee_id,department_name,city

from employees e inner join departments d

on e.department_id=d.department_id     

join locations l

on d.location_id=l.location_id

     #99外连接 outer 外连接

 select employee_id,department_name

 from employees e left outer join departments d

 on e.department_id=d.department_id

select employee_id,department_name

from employees e right outer join departments d

on e.department_id=d.department_id