Hi,

NULL means unknown and is a state, not a value. How are you going to know
what's left when you don't know how much you've subtracted? Using NULL as a
value is not recommended and will give you the kind of trouble you seem to
experience. My advice would be to replace those NULLs with a value wherever
appropriate and if they really are unknown, but in certain situations are
to be treated as a value - write a stored procedure.

There may well exist some UDFs to help you out solving things differently -
I've just never needed them and don't know about their existence.

Good luck with your NULLs,
Set

>Hello..
>we have serious problem of checking null values. is there any
>solutions for it.
>We have written query and in that query i am doing minus value from
>the another value like.
> select val1 - val2 from table.
>val1 has value but val2 is "NULL" so i get null value finaly.
>"In oracle NVL function to solve the problem so if any function in
>Firebird Interbase 6 to solve the problem..?"