RE: Sub-query in order by clause

Jacques,  

As I believe has been pointed out already it may possibly be more efficient if dept is very small and emp is very large (especially if there are filters and a join would be done before a filter was applied). Alternatively it may be that Oracle believe it is more intuitive to people with no preconceived ideas.  

Iain Nicoll
-----Original Message-----
Sent: 04 April 2003 20:24
To: Multiple recipients of list ORACLE-L

Why would you do that instead of
SELECT emp.deptno, empno, ename
FROM emp a, dept b
WHERE dept.deptno = emp.deptno
order by dept.deptname ;

> -----Original Message-----
> From: Nicoll, Iain [ mailto:IAIN.D.NICOLL_at_saic.com
<mailto:IAIN.D.NICOLL_at_saic.com> ]
>
> Don't really know but couldn't it be useful if you had
>
> ORDER BY ( SELECT deptname FROM dept
> WHERE dept.deptno = emp.deptno)
>
>
> -----Original Message-----
> From: Ashish [ mailto:ash03_at_att.net <mailto:ash03_at_att.net> ]
>
> In Oracle 9.2.0.1, you can now order by using a single-row subquery
> Here is an example:
>
> SELECT emp.deptno, empno, ename
> FROM emp
> ORDER BY ( SELECT deptno FROM dept
> WHERE dept.deptno = emp.deptno );
>
> The question I have is what is the usefulness of this? Under which
> circumstances
> this can be used?

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Author: Nicoll, Iain
  INET: IAIN.D.NICOLL_at_saic.com

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