join problem...

Hi,

i'm trying to extract some info from system catalog tables.
documentation says that i should join columns of different data type.
that is int2[] with int2, array with integer.
how can i make this join work?

thanks

http://www.postgresql.org/docs/7.4/static/catalog-pg-constraint.html

      conkey int2[] pg_attribute.attnum If a table constraint, list of
columns which the constraint constrains