Claudio,

>It's time that you invest efforts reading LangRef, man.

don't think I am lazy and don't want to study.

Reference is reference. It means you already know what to look for.

You don't learn a foreign language by studying the vocabulary.

I have gone thru the whole IB tutorial, and also I have read "Database
Developer's Guide with Delphi 2" by Ken Henderson, but when you go into
practice, you always seem to miss a little detailt that prevents you from
completing the code.

>This is the same command that Lucas Franzen gave you. Exactly the same,

but with two columns.

actually I already knew that command.

What I didn't know is that a constraint is not checked if the field is NULL.

Maybe my fantasy is not wild enough, but how could I know that ?

Also, what is natural to you (i.e. that a command good for one column is
good for 2 or more column) is not natural to me (at least, not yet).

I thought that when using 2 or more columns one had to use triggers or -
God forbid - stored procedure.

I guess that IB lacks a good tutorial.

Can you point me to a good source of IB code ?

Thank you

Duilio Foschi