foreign key help - Mailing list pgsql-general

I am building a database that has about 20 fields in various tables that
  I would like to constrain to a small group (<=5) of choices.  Rather
that refer to 20 seperate tables, I would like to refer to 1 table that
contained category and choice fields.

for example

choices table

category | choice
-----------------
color    | red
color    | green
size     | small
size     | big
shape    | circle
shape    | square

item table

item     |  shape
-----------------
box      |  constrain to choices(choice) where category='shape'



Is there an easy way to do this, or is it better to have many
choices_category tables?

Thanks,

Dale