In you original example, the banks record cannot be deleted if a
customer is using it and one cannot be added or updated without a
bank record existing.

However you will have add the constraint 'not null' on IdBank in
customers to prevent a record being posted with a null value


--- In firebird-support@yahoogroups.com, "Maurizio P."
<mauriz_po@...> wrote:

>
> Thanks for Answers
> now i know more about foreign keys ,
> i have a question refering to the two tables of my previous message

(tBanks , tCustomers) :

> i want the user cannot delete a tBanks record if it exists in the

tCustomers table .

>
> No other constraints , e.g. a tCustomer record can be not

connected to any tBanks record .

> ...using foreign keys , i can't leave a tCustomer record without a

tBanks record connected .

>
> can i do that only with triggers ?
>
> thanks
>
> Maurizio
>
> [Non-text portions of this message have been removed]
>