Oracle Today - Latest Comments in Relational algebra: division in sql

Re: Relational algebra: division in sql

rent limousine — Fri, 11 Sep 2009 05:22:33 -0000

The post is so interesting and easy to understand. Relational algebra and its step by step solution has made the sql unproblematic and simple. Thank you for sharing.

Re: Relational algebra: division in sql

hypnosis.course — Thu, 19 Mar 2009 14:43:49 -0000

There’s also this alternative approach which is usually more efficient:

SELECT name
FROM Student
WHERE SID IN ( SELECT SID
FROM Register
GROUP BY SID
HAVING COUNT(*) = (SELECT COUNT(*) FROM Course)

Re: Relational algebra: division in sql

buy wow gold — Tue, 18 Nov 2008 14:33:30 -0000

There’s also this alternative approach which is usually more efficient:

SELECT name
FROM Student
WHERE SID IN ( SELECT SID
FROM Register
GROUP BY SID
HAVING COUNT(*) = (SELECT COUNT(*) FROM Course)
)

Re: Relational algebra: division in sql

Aparna — Mon, 07 Jul 2008 01:59:52 -0000

The minus is a very costly affair, and your sql takes 10 times more time to execute than the otherquery you've posted and the one that I used as below:

select sid from (select sid, count(sid) count
from (select distinct sid, pid from catalog) c,
parts p where c.pid = p.pid group by sid) s
where s.count = (select count(distinct pid) from parts)

Re: Relational algebra: division in sql

elai — Thu, 17 Apr 2008 02:25:36 -0000

Yas,

Thanks for your postings and comments regarding Relational Algebra: division in sql!

elai

Re: Relational algebra: division in sql

yas — Thu, 17 Apr 2008 02:21:04 -0000

elai, yours also works.

Re: Relational algebra: division in sql

elai — Thu, 17 Apr 2008 02:09:48 -0000

How about these two sets of queries for division in the case of having all red parts:

select distinct sid
from catalog c, parts p
where c.pid = p.pid and color = 'Red'
group by sid
having count(distinct c.pid) =
(select count(distinct pid)
from parts
where color = 'Red');

select distinct sid
from catalog c1
where not exists (
(select pid
from parts
where color = 'Red')
minus
(slect pid
from catalog c2
where c1.sid = c2.sid));

Re: Relational algebra: division in sql

elai — Wed, 16 Apr 2008 07:06:45 -0000

How about these two sets of queries for division:

select distinct sid
from catalog c, parts p
where c.pid = p.pid
group by sid
having count(distinct c.pid) =
(select count(distinct pid)
from parts);

select distinct sid
from catalog c1
where not exists (
(select pid
from parts)
minus
(slect pid
from catalog c2
where c1.sid = c2.sid));

Re: Relational algebra: division in sql

yas — Thu, 10 Apr 2008 08:08:38 -0000

Sorry, you are using a different sql in your last post. That does not work in 10.2 either.

Re: Relational algebra: division in sql

yas — Thu, 10 Apr 2008 07:32:36 -0000

Laurent, it works in 10.2.0.2. I did not try it on 10G R1.

SQL> r
1 select sid from
2 (select sid,cast(collect(parts_t(pid)) as parts_tt) x from catalog group by sid)
3 where
4* ((select cast(collect(parts_t(pid))as parts_tt) from parts)) submultiset x

SID
----------
1

SQL> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.2.0 - 64bi
PL/SQL Release 10.2.0.2.0 - Production
CORE 10.2.0.2.0 Production
TNS for Solaris: Version 10.2.0.2.0 - Production
NLSRTL Version 10.2.0.2.0 - Production

Re: Relational algebra: division in sql

Laurent Schneider — Thu, 10 Apr 2008 07:27:24 -0000

unfortunately it is quite underused, and it is not working as I expect it to do :
SQL> select sid 2 from catalog 3 group by sid 4 having 5 (select cast(collect(parts_t(pid))as parts_tt) from parts) 6 submultiset 7* cast(collect(parts_t(pid)) as parts_tt) select sid * ERROR at line 1: ORA-00979: not a GROUP BY expression

the ORA-979 makes no sense. I will open a SR and it may be fixed in Oracle 15

Re: Relational algebra: division in sql

yas — Thu, 10 Apr 2008 07:09:54 -0000

Laurent, thanks for the great solution. I did not even know something like submultiset was available.

For the ones interested: submultiset does not exist in 9.2, it comes with 10G R1. It is used to find out if a nested table is a subset of another nested table. Documentation about it is here

Thanks again Laurent.

Re: Relational algebra: division in sql

Laurent Schneider — Thu, 10 Apr 2008 06:48:51 -0000

well, this does not cover when supplier have more pieces than parts. So maybe this :

create or replace type parts_t as object (pid number); / create or replace type parts_tt as table of parts_t; / select sid from (select sid,cast(collect(parts_t(pid)) as parts_tt) x from catalog group by sid) where ((select cast(collect(parts_t(pid))as parts_tt) from parts)) submultiset x;

Re: Relational algebra: division in sql

Laurent Schneider — Thu, 10 Apr 2008 06:25:05 -0000

what about this :
select sid from catalog group by sid having collect(pid) = (select collect(pid) from parts);

well, it is maybe slower

Re: Relational algebra: division in sql

yas — Thu, 10 Apr 2008 02:09:23 -0000

In this case it works. In some other cases it might not. Suppose products have some properties like color. What if I want the suppliers supplying all the red parts?

Re: Relational algebra: division in sql

Ric — Thu, 10 Apr 2008 00:26:58 -0000

I think this different approach should also work:
select sid, count(*) total
from catalog
group by sid having count(*) =
(select count(*) from parts);