select TO_DATE((TO_CHAR(('20'||concat( substr(CONTRACT_START_DATE,8,2),('-'||concat(CASE WHEN LENGTH(CONTRACT_START_DATE) = 2 THEN substr(CONTRACT_START_DATE,4,1) ELSE '0' || substr(CONTRACT_START_DATE,4,1) END ,'-'||substr(CONTRACT_START_DATE,1,2) ))) )) ),'YYYY-MM-DD')AAFROM YYY_KEY-----------------------图片是数据类型