delete a from 表 a
where exists(
select 1 from 表 where id=a.id and 
time <>(select min(time) from 表 where id=a.id )
and 
time <>(select max(time) from 表 where id=a.id )
)

------解决方案--------------------
--显示为两条记录
SQL code

select 
    *
from 
    timerecords a
where
    sign_time=(select max(sign_time) from timerecords where card_id=a.card_id and datediff(d,sign_time,a.sign_time )=0)
or
    sign_time=(select min(sign_time) from timerecords where card_id=a.card_id and datediff(d,sign_time,a.sign_time )=0)