Hello Martin and Luc

> NULL means the state of 'unknown'.
>
> value + unknown = unknown

But why select sum(d_imip) from transaksi will give me the right result ?

> If you want your empty columns to behave as 0, better make sure they are

0.

No. For some reason this field is null permited.

> If this behaviour is only wanted for the sake or summing the fields, try

the

> new Firebird User Defined Functions - see www.firebirdsql.org for more

info

> on those (release notes for FB1)

What kind of UDF do you mean ?

regards

Bayu