select username from a where a.type=0 and a.type<>1 and to_date(a.time ,‘yyyy-mm-dd’) =‘2022-06-04’;
union all
select username from a where a.type=1 and a.type<>0
and to_date(a.time ,‘yyyy-mm-dd’) =‘2022-06-04’
;

type值为0代表签到，为1代表签退。

select username
from 考勤表
where time >=&begin_time
and time < &end_time
group by username
having count(distinct type)<2;

补充描述一下问题：我觉得实际场景更多的是时间跨多天而不是只查某一天，通常是考勤员每周一去拉上周的数据，或者是其他的时间范围。

select trunc(time) dt,username
from 考勤表
where time >=&begin_time
and time < &end_time
group by username,trunc(time)
having count(distinct type)<2;