Joins between int and int[]

Hi,

I want to use the system catalog tables/views to query some things, and
one of the queries I have to do is joining pg_attribute and pg_constraint to
know what constraint belongs to which table.attribute. My question is how
can I write the join clause between a int (pg_attribute.attnum) and int[ ]
(pg_constraint.conkey).

The query is:

select relname, attname, attnotnull, atthasdef

from pg_class as pc

inner join pg_attribute as pa

on pc.oid=pa.attrelid

inner join pg_constraint pcons

on pc.oid=pcons.conrelid

and pa.attnum = pcons.conkey -------> the problem

Thanks!!!