Article View: borland.public.interbase.sql
Article #11129Avoid deletion of master with details
From: Stig Andersen
Date: Mon, 16 Dec 2002 22:06
Date: Mon, 16 Dec 2002 22:06
53 lines
2238 bytes
2238 bytes
Hi,
How do I avoid that a master record is deleted if it has details (on the
server side):
BUT instead of being deleted it should instead be "marked obsolete"
For example
create MASTER_TABLE
(
MASTER_ID integer not null primary key,
OBSOLETE smallint /*, ("Boolean")
M_Field2 something*/
);
create DETAIL_TABLE
(
DETAIL_ID integer not null primary key,
MASTER_ID integer/*,
D_Field1 something*/
);
alter table DETAIL_TABLE add foreign key (MASTER_ID)
references MASTER_TABLE(MASTER_ID) on cascade update on delete update;
My solution (which is NOT ideal):
create Exception CANNOT_DELETE 'Sorry, no delete';
set term ^;
create trigger MASTER_TABLE_BD for MASTER_TABLE
active before delete
as
declare variable CNT integer;
begin
SELECT COUNT(*)
from DETAIL_TABLE
where DETAIL_ID = OLD.DETAIL_ID
into :CNT;
if (:CNT > 0) then
exception CANNOT_DELETE;
/* the following does not work like I had imagined:
WHEN ANY do
begin
update MASTER_TABLE
set OBSOLETE = 1
where MASTER_ID = OLD.MASTER_ID;
end */ /*see what I try to do? - but the row gets deleted
anyway!!*/
end^
set term ;^
I know it can be done in a TIBDataSet, but that is on the client, not the
Database.
Any suggestions are much appreciated.
Sincerely
Stig Andersen
Technical Details
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