DB structure question

[Anon]

Hi Guys,
I have a mySQL DB. In this database i have a table called "categories". This table has several fields, one of which is called "pref". "pref" will always have a value between 1 - 5.
In relation to "pref" i want to add 3 more fields, eg. name, email and expiry_date.
But because only some "pref"s have name, email etc values i want to create a new table that holds the name, email and expiry_date values otherwise the categories table will have wasted space.
Can anyone tell me the structure i will need to relate the ocategory table to the new one?
The category table contains a CatID field that is auto_increment and primary key.
Any ideas?
micmac

[bastien]

table_categories
CatID integer (1), primary, autonumber
catDesc text (50)

table_users
id integer, primary, autonumber
name text(50)
email text(100)
expiry_date date
CatID integer (1)

hth

Bastien