case when then 中判断null的方法

--下列SQL无效
SELECT CASE MAX(T.CREATE_TIME) WHEN NULL THEN TO_DATE('2019-03-05 00:00:01','yyyy-MM-dd hh24:mi:ss') ELSE  MAX(T.CREATE_TIME) END AS CREATE_TIME FROM  rpt_daily_transaction T;

--需要用下面SQL
SELECT CASE  WHEN MAX(T.CREATE_TIME)  IS  NULL THEN TO_DATE('2019-03-05 00:00:01','yyyy-MM-dd hh24:mi:ss') ELSE  MAX(T.CREATE_TIME) END AS CREATE_TIME FROM  rpt_daily_transaction T;