Choice of left or right outer join

Question

Hi Experts,
I have a two tables like named as emp demo
desc emp
empname varchar2(50)
empid number
desc demo
empname varchar2(50)
empid number
when i implement the below quries i'm getting the same o/p.
queries like
select e.ename from emp e left outer join demo d on (e.empid=d.empid);
select e.ename from demo d right outer join emp e on (d.empid=e.empid);
In this case which query is most prefer
Thnks in advance
H

Answer 1

Hi,
943338 wrote:
Hi Experts,
I have a two tables like named as emp demo
desc emp
empname varchar2(50)
empid number
desc demo
empname varchar2(50)
empid number
when i implement the below quries i'm getting the same o/p.Right. You're getting the same error, because there is no ename column. If you change ename to empname, then you'll still get the same results, because
x LEFT OUTER JOIN y    ON zis equivalent to
y RIGHT OUTER JOIN x    ON zin results and performance.
queries like
select e.ename from emp e left outer join demo d on (e.empid=d.empid);
select e.ename from demo d right outer join emp e on (d.empid=e.empid);
In this case which query is most preferBoth are equally efficient.
Since most people never use RIGHT OUTER JOIN, it might make maintenance eaiser if you don't use it, either. I would use LEFT OUTER JOIN.