MaryAnn,
the best way to understand rownum is to do the following:
SQL SELECT ROWNUM, GENDER
2 FROM (SELECT ROWNUM, GENDER
3 FROM EMP2
4 WHERE ROWNUM = 20)
You will quickly see that, no matter how you order the result set, the first
record returned is rownum #1,
Only less and = queries with regards to rownum are supported.
RF
-Original Message-
To: Multiple recipients of list ORACLE-L
Sent: 7/9/2003 11:19 AM
I definitely dont fully understand ROWNUM yet,
and you guys so far provided more info than a couple of books
by Oracle, that I have
To add on to my previous comments, change your code a bit:
SQL SELECT RN, GENDER
2 FROM (SELECT ROWNUM RN, GENDER
3 FROM EMP2
4 WHERE ROWNUM = 20)
5 WHERE RN 10;
-Original Message-
To: Multiple recipients of list ORACLE-L
Sent: 7/9/2003 11:19 AM
I
Each row that is retrieved from the database that matches the WHERE condition is
placed in a result set. The sequence within the result set is the value in the
pseudocolumn ROWNUM. If Oracle is using a full-table scan, the first row of the first
block is the first in the result set and is
Its obvious I hadnt fully understood ROWNUM yet, as you see
we are learning bits and pieces as we go along.
Help me out here, will you? Talk to me like I'm a 10-year old, its ok.
MaryAnn, the best way to understand rownum is to do the following:
SQL SELECT ROWNUM, GENDER
2 FROM
Think of it this way: when Oracle builds a result set, it goes
into the table and tries to qualify the records in the table
by evaluating the where clause; if the record does not qualify,
the record will not appear in the result set, if the record does
qualify, then the record will be returned in
THATS THE ONE!!! THAT DID IT!!!
--- Freeman Robert - IL [EMAIL PROTECTED] wrote:
To add on to my previous comments, change your code a bit:
SQL SELECT RN, GENDER
2 FROM (SELECT ROWNUM RN, GENDER
3 FROM EMP2
4 WHERE ROWNUM = 20)
5 WHERE RN 10;
The last
I definitely dont fully understand ROWNUM yet,
and you guys so far provided more info than a
couple of books
by Oracle, that I have here. For a second I thought
I'm
beginning to get it, but the queries suggested
produced no results...
SQL SELECT ROWNUM, GENDER
2 FROM (SELECT ROWNUM,
Mary Ann,
Assume that the rows are selected in random order. Primary Keys and Order By exist
for ordering and qualifying your data. If you just select * from EMP2, most likely
the rows willl come back in the order that they were inserted, but this is not
necessarily true, especially if
Oracle does not guarantee the order in which records are retrieved (read in
from the disk or data buffers) nor does Oracle guarantee the order in which
records are presented to you unless you specify an ORDER BY. The ROWNUM is
assigned after Oracle has selected the record to appear in the result
Can the inner-outer idea be extended to an update?
UPDATE EMP2
SETGENDER = 'F'
WHERE GENDER = ' '
ANDROWNUM BETWEEN 10 AND 20;
That does NOT work, because as we explained the returned rows
are numbered starting from 1, and so rownum never really matches
a 10 or 20 or anything
IF you are looking to break up the update into more 'manageable' pieces, here is a
thought...
UPDATE EMP2
SET GENDER = 'F'
WHERE GENDER = ' '
AND ROWNUM = 100;
UPDATE EMP2
SET GENDER = 'F'
WHERE GENDER = ' '
AND ROWNUM = 100;
*Since the first 100 records have already been updated, the second
just what is it you want to return in your query?
If the query results are to be displayed a chunk at a time on a web page
then you should give strong consideration to using OCI and implementing
scrollable cursors with the OCIStmtFetch2() function and its
OCI_FETCH_NEXT, OCI_FETCH_PRIOR,
PROTECTED]
Date: 2003/07/09 Wed PM 01:34:24 EDT
To: Multiple recipients of list ORACLE-L [EMAIL PROTECTED]
Subject: RE: ROWNUM - Can the inner-outer idea be extended to an update?
Can the inner-outer idea be extended to an update?
UPDATE EMP2
SETGENDER = 'F'
WHERE GENDER
just do
select rownum, col1,col2, from
table1
-Message d'origine-De: Santosh Varma
[mailto:[EMAIL PROTECTED]Envoyé: mercredi 19 mars 2003
09:44À: Multiple recipients of list
ORACLE-LObjet: Rownum
Hello list,
I wanted to know
the concept of Rownum.. Is it
Santosh,
Good question. Actually these 2 are not related.
Rowid is an actual attribute assigned to each row of a table and is unique.
Rownum is logically assigned to rows returned in a query (nothing to do with the
table). It is assigned sequentially as rows are returned (meaning if you can't
no,
rownum is a sequential number whereas rowid
is a pointer to the row of the table within the database.
-Original
Message-From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]On
Behalf Of Santosh VarmaSent: Wednesday, March 19, 2003 4:44
AMTo: Multiple recipients of list
Darrell Landrum,ÄúºÃ£¡
thanx for your explaination.
I wonder :whether i can judge the select return.
I find the rowNUM is not 0, is right?
=== 2003-03-19 05:03:00 ÄúÔÚÀ´ÐÅÖÐдµÀ£º===
Santosh,
Good question. Actually these 2 are not related.
Rowid is an actual attribute
No. It is not similar to a rowid.
It is just a pseudo sequential number assigned to the rows in the result set (after
the result set is prepared) from the query.
- Kirti
-Original Message-
Sent: Wednesday, March 19, 2003 3:44 AM
To: Multiple recipients of list ORACLE-L
Hello list,
That's correct, there's no rownum of 0.
ex.
SQL select rownum, username from dba_users;
ROWNUM USERNAME
-- --
1 SYS
2 SYSTEM
3 OUTLN
4 OEM_DLAND
5 DBSNMP
6 HR
7 PM
8 DLANDRUM
9
Thanks to all who replied to
me.
Now it is clear..
santosh
-Original Message-From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]On Behalf Of John BlakeSent:
Wednesday, March 19, 2003 7:15 PMTo: Multiple recipients of list
ORACLE-LSubject: RE: Rownum
no,
rownum
Post your query
-Original Message-
Sent: Thursday, August 29, 2002 9:23 PM
To: Multiple recipients of list ORACLE-L
I've been given a query to investigate. The performance varies
extremely depending on whether the entire result set is fetched or a
ROWNUM n clause is attached; that
Holes in your extents/segments. Normal. You get this after repeated
updates/deletes/inserts.
ltiu
Paul Baumgartel wrote:
I've been given a query to investigate. The performance varies
extremely depending on whether the entire result set is fetched or a
ROWNUM n clause is attached; that
Hi Paul,
How's going?
Maybe there are other criteria's that limits the result set to only
return 24 rows?
Richard Ji
-Original Message-
Sent: Thursday, August 29, 2002 11:53 AM
To: Multiple recipients of list ORACLE-L
I've been given a query to investigate. The performance varies
Actually. Scratch my previous email on this matter.
We have seen this problem before and I couldn't figure out how to fix it.
ltiu
Paul Baumgartel wrote:
I've been given a query to investigate. The performance varies
extremely depending on whether the entire result set is fetched or a
ROWNUM
As we all know, ROWNUM is *usually* assigned when rows are
read into the cache, before sorting;
Always
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
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Author: Naveen Nahata
INET: [EMAIL PROTECTED]
Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051
Paul Baumgartel wrote:
I've been given a query to investigate. The performance varies
extremely depending on whether the entire result set is fetched or a
ROWNUM n clause is attached; that makes sense to me. What doesn't
make sense is the following: if we add WHERE ROWNUM 50, the query
Title: RE: ROWNUM strangeness?
show the full sql please, perhaps its how you are grouping your
conditions
Paul Baumgartel wrote:
I've been given a query to investigate. The performance varies
extremely depending on whether the entire result set is fetched or a
ROWNUM n clause
Paul,
It's because of how ROWNUM is interpreted.
The first query only returned the first 50 rows it found and you got 24 that
passed the rest of your criteria.
The second query returned 1000 rows of which only 336 passed the rest of
your criteria.
Makes perfect sense to me. This is why
I believe you have ROWNUM confused with ROWID.
--- ltiu [EMAIL PROTECTED] wrote:
Holes in your extents/segments. Normal. You get this after repeated
updates/deletes/inserts.
ltiu
Paul Baumgartel wrote:
I've been given a query to investigate. The performance varies
extremely
Actually, ROWNUM has nothing to do with
extents/segments/inserts/updates/deletes. It is all about access paths. The
solution posted makes sense as ROWNUM can be affected by many subsequent
operations.
-Original Message-
Sent: Thursday, August 29, 2002 11:04 AM
To: Multiple recipients of
To be exact...
Rownum is sequentially assigned for each row that meets the predicate. If
the row does not match the predicate condition, it is discarded and not
assigned a rownum. Below is an example using our friendly EMP table.
As for sorting, rownum is assigned before any sorting. However,
I agree. I got confused and my second email to disregard my erroneous
first emai on this matterl was apparently shot down by the mail filters
so it never got to you guys in time.
Sorry for the confision.
ltiu
Fink, Dan wrote:
Actually, ROWNUM has nothing to do with
Yes sir.
Paul Baumgartel wrote:
I believe you have ROWNUM confused with ROWID.
--- ltiu [EMAIL PROTECTED] wrote:
Holes in your extents/segments. Normal. You get this after repeated
updates/deletes/inserts.
ltiu
Paul Baumgartel wrote:
I've been given a query to investigate. The
It is not the predicate that causes the behavior, but the distinct. I'm
taking an educated guess here, so please correct me if I am wrong.
As the row is read, the predicate is applied. If the row matches the
predicate, a rownum is assigned and it is saved as part of the result set.
Once the
As for sorting, rownum is assigned before any sorting. However, if the data
is read via an index, the rownum appears to be assigned after the sort.
Dan,
I wouldn't say that. What *appears* is the sort, which doesn't take
place since data is fetched in sorted order. Rownum is assigned in the
Janet Linsy wrote:
Hi,
I have a table like this:
SQL select * from test;
ID PRICE
-- --
1 1
1 3
1 4
1 5
1 6
I need to get the second largest price and I was
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