자신의 컬럼값으로 update

UPDATE med_article A

    SET A.CONTENTS2 = (

    SELECT B.summary

    FROM med_article B

    WHERE 

    A.article_no = B.article_no 

    );

update med_subscript a

set a.zipcd = (select substr(b.zipcd,0,5) from med_subscript b 

                   where a.SUBSC_SEQ_NUM=b.SUBSC_SEQ_NUM);