Re: Using rowid in a html anchor / select statement

Hans Forbrich wrote:
>
> Thomas J. Kyte wrote:
>
> > 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
> >
>
> Thomas,
>
> Apologies for my incorrect statement. Either I learned it wrong
> or there have been significant changes since I learned it back
> in Oracle v4/v5 days.
>
> /Hans

ROWID's do change!
It is true that a ROWID stays the same for a record but... ...all ROWID's are re-assigned when a table is export w/compress and then imported. ...If a record is deleted it's ROWID can be reused. This will not happen immediately but will happen eventually.

Dave Received on Tue Oct 01 1996 - 00:00:00 CEST