There is a simple example about foreign key.

Create Table Master
(Id Integer nor null,
Description Varchar(20),
Primary Key (Id)
);


Create Table Detail
(Id Integer nor null,
Recno Integer not null,
Description Varchar(20),
Field1 Varchar(50),
Field2 Varchar(100),
Primary Key (Id,Recno),
Foreign Key (Id) References Master(Id) On DELETE CASCADE ON UPDATE
CASCADE);


if you delete a record from master table, Foreign key will delete records
from detail table.
Foreign key executes this sql statement
Delete from detail where id = old.id

if you change a record from master table, foreign key will update records
from detail table.
Foreign key executes this sql statement
Update detail
set
id = new.id
where id = old.id



I think that
Foreign key is slowing the database.
I rearly use foreign key.
I wrote After Delete trigger and After Update trigger to master table.
my customers are using this type database (without foreign key) for 2 years.
there wasn't any problem.
There won't be any problem.




Ibrahim Bulut
Software Developer
Republic of Turkey

----- Original Message -----
From: "Nataraj S Narayanan" <nataraj@...>
To: <ib-support@yahoogroups.com>
Sent: Tuesday, April 09, 2002 2:01 PM
Subject: Re: [ib-support] Mass deletion


> On Tue, 9 Apr 2002, Nick Upson wrote:
>
> Hi
>
> Just created and tried a trigger in drug_bill. The following is the body
> of the trigger
>
> BEGIN
>
> delete drug_bill_item where drug_bill_item.bill_id=bill_id;
>
> END;
>
> The result is startling!! it empties the drug_bill_item table when i
> delete records in drug_bill.
>
> Something wrong with the trigger?
>
>
> > Have you tried having a before delete trigger on drug_bill that
> > deletes the appropiate drug_bill_item.
> > Then you can just do:
> >
> > delete from Drug_bill Where Bill_Date between '01-JAN-1999' and
> > '31-DEC-1999')
>
>
>
>
> >
> >
> > >From: Nataraj S Narayanan <nataraj@...>
> > >The Tables to delete data are Drug_Bill and Drug_Bill_Item ,where the
2nd
> > >table has a foriegn key of Drug_Bill by name Bill_Id.
> > >
> > >As said by Helen I gave the command 'Delete from Drug_Bill_Item where
> > >Bill_id in (select Bill_id from Drug_bill Where Bill_Date between
> > >'01-JAN-1999' and '31-DEC-1999')
> > >
> > >
> > >Unfortunately, the operation takes aeons (7 hours) to complete. The gdb
is
> > >119
> > >Mb.
> >
>
> --
> Nataraj S Narayanan
> Synergy Info Systems
> Kochi,India-683 503
> Ph:95 484 557244
>
>
>
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