Re: RE: Delete + Insert versus Update

Another (maybe not so) subtle difference is that DELETE/INSERT will hit *every* index, while updates will touch only indexes on changed columns. (Won't they? I really shouldn't be so daring with such statements on a mailing list like this one!)

If a table is heavily indexed, this could make a very substantial difference.

(Heaven help me, I have actually *seen* tables with more indexes than columns!)

Anyway, I'm walking into the middle of this thread without even seeing the original question. Apologies if I'm off topic... (Or just plain hallucinating.)

Cheers,
-- Mark.

• Original Message ----- From: oracle-l-bounce_at_freelists.org Date: Thursday, February 16, 2006 9:02 am Subject: RE: Delete + Insert versus Update

> Plus, if INSERT/DELETE executed from the app, it's an additional
> trip to
> the database through SQL*Net, when comparing to UPDATE.
>
> Igor
>
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org
> [oracle-l-bounce_at_freelists.org] On Behalf Of Ric Van Dyke
> Sent: Thursday, February 16, 2006 10:54 AM
> To: norman.dunbar_at_environment-agency.gov.uk; oracle-l_at_freelists.org;
> peters_at_mitre.org
> Subject: RE: Delete + Insert versus Update
>
> Also don't forget all the redo generated.
>
> A delete and reinsert could easily be 4+ times more expensive then an
> update.
>
> Ric Van Dyke
> Hotsos Enterprises
> Cell 248-705-0624
> -----------------------
> Hotsos Symposium, be there:
> http://www.hotsos.com/portal/events/SYM06
> -----Original Message-----
> From: oracle-l-bounce_at_freelists.org
> [oracle-l-bounce_at_freelists.org] On Behalf Of Norman Dunbar
> Sent: Thursday, February 16, 2006 10:34 AM
> To: oracle-l_at_freelists.org; peters_at_mitre.org
> Subject: Re: Delete + Insert versus Update
>
>
> Peter,
>
> My initial, off the top of my head, thought is simple :
>
> in an UPDATE, the undo holds the before 'image' of the changed
> columns.In a DELETE, the whole row is in the undo.
> An INSERT, as far as I remember, holds the rowid as all it has to
> do is
> delete the row.
>
> So straight away there's a difference.
>
> As for indexes, an UPDATE is a DELETE/INSERT anyway.
>
> As ever, untested (yet) !
>
>
> Cheers,
> Norman.
>
>
>
>
> Norman Dunbar.
> Contract Oracle DBA.
> Rivers House, Leeds.
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