I want to generate qualify_flag as '1' always when device_end_dt = '9999-12-31 23:29:59'. If it is 
 not '9999-12-31 23:29:59' then if DEVICE_END_DT + 1 day = CREATION_DATE then qualify_flag is 0 else 1. 
DEVICE_END_DT is TIMESTAMP(0), CREATION_DATE  is TIMESTAMP(6). 
CREATION_DATE column doesn't have any value which is '9999-12-31'.

下面的case语句失败，日期无效，看起来像是'9999-12-31'不知怎么来了，'9999-12-31'+1）模棱两可。

select
case When 
        Cast(DEVICE_END_DT AS DATE) <> CAST('9999-12-31' AS DATE) 
            THEN
                case when CAST((Cast(DEVICE_END_DT AS DATE) + 1) AS DATE) = Cast(CREATION_DATE AS DATE)
                        then 0
                        else 1
                end
case when   
        Cast(DEVICE_END_DT AS DATE) = CAST('9999-12-31' AS DATE) 
            THEN
                            1 
end 
end as qualify_flag
 FROM ABC;