update 子查询隐含风险

update examinees s

   set (s.birthdate,

        s.issuecertdate,

        s.acceptgradedate,

        s.lastmodifieddate) = 

(select  to_char(t.birthdate, 'yyyy/mm/dd'),

        to_char(t.issuecertdate, 'yyyy/mm/dd'),

        to_char(t.acceptgradedate, 'yyyy/mm/dd'),

        to_char(t.lastmodifieddate, 'yyyy/mm/dd') from examinees_impto_zt t where

         s.examineeid = to_char(t.examineeid))

 where exists(select 1 from examinees_impto_zt b where s.examineeid = to_char(b.examineeid));