UPDATE contractnotice
SET "supplierABN" = subquery."supplierABN"
FROM (SELECT
        "CNID",
        a."supplierABN"
      FROM contractnotice
        INNER JOIN
        (SELECT
                      text_mode("supplierABN") AS "supplierABN",
                      lower(regexp_replace("supplierName",'[,\.]','', 'g'))    AS name
                    FROM contractnotice
                    WHERE "supplierABN" IS NOT NULL
                    GROUP BY name) a ON
                                      lower(regexp_replace("supplierName",'[,\.]','', 'g')) = name
      WHERE contractnotice."supplierABN" IS NULL)
  AS subquery
WHERE contractnotice."CNID" = subquery."CNID";