Re: Using rowid in a html anchor / select statement

Thomas J. Kyte wrote:
>
> On Mon, 30 Sep 1996 21:05:54 -0600, Hans Forbrich
> <forbrich_at_tibalt.supernet.ab.ca> wrote:
>
> >Brian Martin wrote:
> >>
> >> Bill Tierney wrote:
 

> >> yes. use a key value instead of rowid. it's not a good thing to
> >> choose for implementation in a state-dependent situation like
> >> a webserver. things could change before the www user sends the
> >> updates or whatever. rowid is a fluid value, not a constant
> >> like a key.
> >
> >Agreed ... the ONLY time you can use ROWID and be guaranteed
> >of results is during a transaction (before commit) after
> >selecting with the 'FOR UPDATE' option. Otherwise you can
> >end up pointing to a row that has been moved.
> >
> >Rowid contains the 'physical' location (file/block/offset) info
> >to find a row quickly. After delete, the rowid is meaningless.
> >Before insert, it is meaningless. After update is MAY be
> >meaningless under a variety of conditions.
> >
> >Hans
>
> Rowid will never change and is *very* useful in html pages for identifying a
> row.
>
> True, before insert, a rowid doesn't exist and after a delete it is meaningless
> (but I can surely say the same exact thing about a primary key. before insert--
> meaningless. after delete-- meaningless).
>
> Rowids exist with the row for as long as the row exists. You must delete and
> then re-insert a row to get a different rowid. Oracle Forms is completely
> reliant on the rowid and would completely fail if it changed. Oracle basic
> replication (r/o snapshots) is completely dependent on rowid and would fail if
> it changed. Oracle indexes are completely dependent on rowid and would fail if
> it changed (we only update an index entry if you modify the indexed values, we
> would have to modify an index all the times if the rowid could change (but it
> can't))
>
> I like to pass rowids from screen to screen (form to form) cause:
>
> - they are always one column, primary keys can be many columns
>
> - they never contain special html characters like <, >, &, ", ' ', /, etc
> (things that can't be in a url)
>
> - they are the fastest way to get the row back again.
>
> - They are great for implementing drill down.
>
> Here are some quotes from the doc's on the subject:
>
> <quote>
> If a row in a data block is updated so that the overall row lengthincreases and
> the block’s free space has been completely filled, the datafor the entire row is
> migrated to a new data block, assuming the entirerow can fit in a new block.
> Oracle preserves the original row piece of amigrated row to point to the new
> block containing the migrated row; the ROWID of a migrated row does not change.
> </quote>
>
> <quote>
> The ROWID identifies each row piece by its location or address. Onceassigned, a
> given row piece retains its ROWID until the correspondingrow is deleted, or
> exported and imported using the IMPORT andEXPORT utilities. If the cluster key
> values of a row change, the rowkeeps the same ROWID, but also gets an additional
> pointer ROWID forthe new values.
>
> Because ROWIDs are constant for the lifetime of a row piece, it isuseful to
> reference ROWIDs in SQL statements such as SELECT, UPDATE, and DELETE. See
> “ROWIDs and the ROWID Datatype” onpage 6–9.
> </quote>
>
> <quote>
> A row’s assigned ROWID remains unchanged unless the row isexported and imported
> (using the IMPORT and EXPORT utilities). When you delete a row from a table (and
> then commit theencompassing transaction), the deleted row’s associated ROWID can
> beassigned to a row inserted in a subsequent transaction.
> </quote>
>
> Thomas Kyte
> Oracle Government
> tkyte_at_us.oracle.com
>
> http://govt.us.oracle.com
>
> ---- Check out Oracle Governments web site! -----
> Follow the link to "Tech Center"
> and then downloadable Utilities for some free software...
>
> -------------------
> statements and opinions are mine and do not necessarily
> reflect the opinions of Oracle Corporation

Small note: RowId would change after export-import (with probability almost 100%). This is only case I know RowId change for particular row.

-- 
********************************************************
*        Everything above is only my opinion           *
********************************************************
*						       *
* If you see a lion in a cage and sign says "elephant" * 
*                      ,                               *
*           DO not belive your eyes !                  *
*       (Kozma Prutkov. (informal translation))        *
*                                                      *
********************************************************