A foreign key constraint specifies that the values of a column (or group of columns) must match the values in some row of another table. This is called the referential integrity of two related tables.
The FOREIGN node displays information on all foreign keys created in the table
SELECT oid, conname,
pg_catalog.pg_get_constraintdef(r.oid, true) as condef,
conrelid::pg_catalog.regclass AS ontable
FROM pg_catalog.pg_constraint r
WHERE r.conrelid = $$TABLEOID
AND r.contype = 'f'
AND conparentid = 0
ORDER BY conname