Re: Checksum on row
Date: Mon, 25 Oct 1999 15:04:43 +0200
Message-ID: <7v1kk2$ojt$1_at_oceanite.cybercable.fr>
You can add a trigger on insert and update to calculate your checksum:
create or replace trigger tr_ud before insert or update on <table>
for each row
declare
chksum number;
begin
/* calculate the checksum using :NEW.col1, :NEW.col2, :NEW.col3, ... */
chksum := <my function> (:NEW.col1, :NEW.col2, ...);
/* set the checksum column of the inserted or updated row */
:NEW.checksumcol := chksum;
end;
/
When you add or update a row, the checksum is then calculated and the checksum column is set.
To check the row on the select statement, you have to create a function to verify the checksum, something like that:
create or replace function check_t (id rowid) return number is
/* return 1 if checksum OK, 0 otherwise */
row <table>%rowtype;
chksum number;
begin
select * into row from <table> where rowid=id; /* calculate chksum using row.col1, row.col2, ... */ chksum := <my function> (row.col1, row.col2, ...); if ( chksum = row.checksumcol ) then
return 1;
else
return 0;
end if;
end;
/
and then
select * from <table> where ... and check_t(rowid) = 1;
-- Have a nice day Michel Remco Moolenaar <remco_at_scc.nl> a écrit dans le message : 381442E8.56A83152_at_scc.nl...Received on Mon Oct 25 1999 - 15:04:43 CEST
> Good afternoon,
>
> I want to do the following on rows of a table:
> - When a row is added calculate some sort of checksum (MD5?) of the
> contents of the row.
> - Save this value in a dedicated column of the same row.
> - Use this checksum to calculate the correctness of the row (including
> detail rows).
>
> How do I do this using standard methods. This is for a international
> project, so I need standard tools (like MD5).
>
> Thanks in advance,
>
> Remco Moolenaar
>
> --
> Remco Moolenaar mailto:remco_at_scc.nl
> SCC Internetworking & Databases http://www.scc.nl/
> Amsterdam, The Netherlands mailto:remco_at_bsdapps.org
>
> Maintainer of the BSD Applications database at http://www.bsdapps.org/
>
>