[postgis-users] Adding constraint

[Piotr Pachół]

Hello,
Is it possible to add constraint to second attribute of table only in 
the situation when first attribute of table equals specified value ?
I give an example:

CREATE TABLE test (
     attrib_1 text,
     attrib_2 text
);
INSERT INTO test VALUES ('AAA', 'QQQ');
INSERT INTO test VALUES ('BBB', 'PPP');


So is it possible to add  constraint (for instance NOT NULL) to attrib_2 
column if attrib_1 = 'AAA'

Regards,
Piotr