Another question I am asking, it might seem very trivial and easy
but being a new user of FireBird (the latest release) installed and
connected, I do suffer some headaches regarding this. I have created
a database (successfully), added the tables I required and got stuck
when trying to do the following.

CREATE TABLE contacts(
CONTACT_CODE VARCHAR(10) NOT NULL,
CONTACT_NAME CHAR(50) NOT NULL,
CONTACT_GENDER VARCHAR(1) NOT NULL,
CONTACT_NATIONALITY VARCHAR(5) NOT NULL,
CONTACT_PHONE VARCHAR(15)[3]
PRIMARY KEY(CONTACT_CODE)
);
CREATE INDEX contactname ON contacts(CONTACT_NAME);
ALTER TABLE contacts
ADD CONSTRAINT fk_nationality
FOREIGN KEY (CONTACT_NATIONALITY)
REFERENCE countries(COUNTRY_CODE)
ON UPDATE CASCADE;

Now my first problem is not creating the table but when trying to
create another constraint where the CONTACT_GENDER must either be M
or F. I have created a constraint with INTEGER where I could specify
a range between two numbers but I am stuck with forcing either one
of two characters.

The second problem, when having an array of values (CONTACT_PHONE) I
wish to have the first value of the array mandatory where the two
remaining values are optional. How do I define that in the table? If
I declare the field as NOT NULL will this not cause all three the
values to be mandatory? Is the only solution to have this validation
done in code or is it possible to define it within the table
definition?

Many thanks,
Antz