constraint/restrict

hi there,

with two tables i want to make some constraint-restrictions

create table address ( id serial,  country_id int4, ....);
and
create table country (id serial, ...);

to make sure that now country-row is deleted if there is still a country_id 
in address table.

e.g.

address: 1, 2, ...
country: 2, ...

now country wouldn't be allowed to be deleted. 

how to do that?

thanks fo help

olaf
-- 
soli-con Engineering Zanger, Dipl.-Ing. (FH) Olaf Marc Zanger
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