Find referenced field(s) of foreign key constraint

Question

I have a table Users with a field called org_id which is a foreign key to a table organisation, with primary key field organisation_id. Knowing the table name (users) and the field name (users.org_id), is there a query that can tell me the name and field that org_id references?

I've found a Stackoverflow post similar to this where a query was provided to determine the referenced table name, but I also need to know the field name that is referenced:

SELECT c.confrelid::regclass::text AS referenced_table
  ,c.conname AS fk_name
  ,pg_get_constraintdef(c.oid) AS fk_definition
  FROM   pg_attribute a 
  JOIN   pg_constraint c ON (c.conrelid, c.conkey[1]) = (a.attrelid, a.attnum)
  WHERE  a.attrelid = '"Schema"."Users"'::regclass   -- table name
  AND    a.attname  = 'org_id'                           -- column name  
  AND    c.contype  = 'f'
  ORDER  BY conrelid::regclass::text, contype DESC;

So the above query would return the name of the table (organisation), the fk name and fk definition. Is there a way to also get the name of the field that is referenced? I know I could probably perform another query to determine the name of pk given a table but I would like to avoid performing multiple queries for this.

Answer 1

This query adds the referenced column(s) for the foreign key constraint:

SELECT c.confrelid::regclass::text AS referenced_table
      ,string_agg(f.attname, ', ') AS referenced_columns
      ,c.conname AS fk_name
      ,pg_get_constraintdef(c.oid) AS fk_definition
FROM   pg_attribute  a 
JOIN   pg_constraint c ON (c.conrelid, c.conkey[1]) = (a.attrelid, a.attnum)
JOIN   pg_attribute  f ON f.attrelid = c.confrelid
                      AND f.attnum = ANY (confkey)
WHERE  a.attrelid = '"Schema"."Users"'::regclass   -- table name
AND    a.attname  = 'org_id'                       -- column name  
AND    c.contype  = 'f'
GROUP  BY c.confrelid, c.conname, c.oid;

A fk constraint can reference multiple columns. That's the reason for the aggregate function string_agg() in the query.