mysql时分秒格式化

'%Y-%m-%d %k:%i:%S'

比较大小

SELECT

GREATEST(

DATE_FORMAT(IFNULL(sign_time, '0000-00-00'),

'%Y-%m-%d %k:%i:%S'

),

DATE(

IFNULL(buyer_sign_time, '0000-00-00')

)

) insert_time

FROM

`app_buyer_commission_contract`

WHERE

adbp_id = 3546123205723136;