OK, thanks very much for your help.

--- In firebird-support@yahoogroups.com, Helen Borrie <helebor@t...>
wrote:

> At 01:46 PM 13/05/2005 +0000, you wrote:
> >Hi,
> >
> >If a row is deleted from a table, is there any way of recovering

the

> >deleted data? Presumably one method would be to use triggers, which
> >backup any deleted rows to a new table. But are there any features
> >within Firebird that allow data to be recovered?
>
> If you have a business requirement to be able to this, then design
> accordingly. Don't write applications that delete rows from these

tables.

>
> Instead, for tables where it's essential to be able to recover

data,

> include a nullable timestamp column WasDeleted. When the client

app wants

> to request a Delete, make the statement "Update atable set

WasDeleted =

> current_timestamp where...". In all select queries and bulk

updates,

> include "WasDeleted is null" in the WHERE clause. When you need to
> "undelete" a row, just update it again, setting WasDeleted to null.
>
> You can purge these tables periodically by selecting rows on a date-

range

> for WasDeleted and permanently deleting them. If needed, they can

be

> copied to history tables first. From a housekeeping POV, it's a

good idea

> to do these purges just before a backup. As long as you remember

to commit

> the work, the backup will clear out the garbage left behind by the

deletions.

>
> If necessary, write BeforeDelete triggers to test current_user and

except

> out of the deletion if the wrong user is trying to do a physical
> deletion; or set user privileges to determine which users are

allowed to

> delete rows from these tables.
>
> ./heLen