I can't find documentations on the key word join
but I saw examples on the web using it.
I was doing some experiment with it in Oracle hr
schema, where I have table departments
:
deparment_name
manager_id
location_id
A table employees
:
first_name
employee_id
And table locations
:
location_id
city
Query should return the department_name, first_name of the manager of the department, and the city where the department is located.
The code using the keyword join
seem to return the some result in comparison to using the keyword inner join
Code with join
:
select d.department_name, e.first_name,l.city
from departments d
join employees e on d.manager_id=e.employee_id
join locations l on d.location_id=l.location_id
Code with inner join
:
select d.department_name, e.first_name,l.city
from departments d
inner join employees e on d.manager_id=e.employee_id
inner join locations l on d.location_id=l.location_id
Is there a difference between the two condition, or am I just happen to stumble on a situation where they return the same results?
Query expressions 179 7.5 - joined table
3) If a qualified join is specified and a join type is not specified, then INNER is implicit.
INNER
prefix is also optional. Before 9i, Oracle didn't follow ANSI rules, and didn't even support JOIN
syntax.