business-intelligence/data_warehouse/DIM/DIM_DATE_UTILS/DATE_FUNC.sql

CREATE OR REPLACE FUNCTION get_date_primary_key(ts timestamp) RETURNS integer AS $$
   BEGIN
       RETURN 10000 * EXTRACT(YEAR FROM ts) +
              100 * EXTRACT(MONTH FROM ts) +
              EXTRACT(DAY FROM ts);
   END;
$$ LANGUAGE plpgsql;