LOOP funktion find manglende data:

Hej jeg har brug for at finde manglende data i databasen med mange skemaer.
Jeg har en funktion der finder alle felter med teksten '500':
CREATE OR REPLACE FUNCTION pcm_search_columns(
    needle text,
    haystack_tables name[] default '{}',
    haystack_schema name[] default '{}'
)
RETURNS table(schemaname text, tablename text, columnname text, rowctid text)
AS $$
begin
  FOR schemaname,tablename,columnname IN
      SELECT c.table_schema,c.table_name,c.column_name
      FROM information_schema.columns c
        JOIN information_schema.tables t ON
          (t.table_name=c.table_name AND t.table_schema=c.table_schema)
        JOIN information_schema.table_privileges p ON
          (t.table_name=p.table_name AND t.table_schema=p.table_schema
              AND p.privilege_type='SELECT')
        JOIN information_schema.schemata s ON
          (s.schema_name=t.table_schema)
      WHERE (c.table_name='el_div')
        AND (c.table_schema=ANY(haystack_schema) OR haystack_schema='{}')
        AND (t.table_type='BASE TABLE')
        AND (c.column_name='grp')
  LOOP
    FOR rowctid IN
      EXECUTE format('SELECT id FROM %I.%I WHERE cast(%I as text)=%L',
      schemaname,
      tablename,
      columnname,
      needle
      )
    LOOP
      -- uncomment next line to get some progress report
      -- RAISE NOTICE 'hit in %.%', schemaname, tablename;
      RETURN NEXT;
    END LOOP;
END LOOP;
END;
$$ language plpgsql;

select * from pcm_search_columns('500','{}');

det vil jeg meget gerne kombinere med:
select from values((500),(5),.....)
except....?????

desuden vil jeg gerne have at resultatet viser hvilken værdi der exception fra valgte collone???

MVH Mayoh