On Friday 11 July 2003 13:19, [EMAIL PROTECTED] wrote: > So while you are selecting data and before you update, the record could > change. This means someone else could update it and youc ould update over > it without knowing it. This is a bad idea in the database world and is > known as 'disapearing updates'. So you lock the row when you select it. Not > when the actual update is processed.
No, you don't lock a row when you select it. There's no need for a read lock of a row in Oracle to maintain consistency. If Oracle can't produce a consistent row, it throws an ORA-1555. Jared > > Updating inside of cursors is generally a bad idea. Its more code and its > MUCH slower than a straight update statement. Ive seen some publications > stating that it can before to do this way, but Ive tested every case I can > think of and not once was it even close. > > > what is the update statement you want to put inside the cursor? > > > From: MaryAnn Atkinson <[EMAIL PROTECTED]> > > Date: 2003/07/11 Fri PM 04:09:25 EDT > > To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]> > > Subject: RE: full usefullness of CURRENT OF ??? > > > > --- Chris Stephens <[EMAIL PROTECTED]> wrote: > > > Also, the CURRENT OF locks the table so that no one can modify (or > > > even read) it while the transaction is taking place. This guarantees > > > nothing is changing between retrieving values from the cursor and > > > updating the table based on those values. > > > > OK, fair enough. > > > > > The second example has to run the update statement seperately. > > > CURRENT OF can go directly to the row(s) affected. CURRENT OF > > > still has to modify each block header in the table to lock which > > > is a small performance hit. > > > > So CURRENT OF has to lock, so its slower, right? > > Does it have any advantages after all? > > > > >To prevent that you could update by rowid > > > > How? How can I update by ROWID? I was thinking to update > > by PRIMARY_KEY... > > > > > and avoid the header updates. > > > > ... what "header" updates? > > > > thx > > maa > > > > __________________________________ > > Do you Yahoo!? > > SBC Yahoo! DSL - Now only $29.95 per month! > > http://sbc.yahoo.com > > -- > > Please see the official ORACLE-L FAQ: http://www.orafaq.net > > -- > > Author: MaryAnn Atkinson > > INET: [EMAIL PROTECTED] > > > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > > San Diego, California -- Mailing list and web hosting services > > --------------------------------------------------------------------- > > To REMOVE yourself from this mailing list, send an E-Mail message > > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > > the message BODY, include a line containing: UNSUB ORACLE-L > > (or the name of mailing list you want to be removed from). You may > > also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Jared Still INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
