sql考勤

⑴ 如何在sql数据库里再增加一个打卡时间，以图片数字为列

用sql语句
alter table 考勤表 ADD clock time time stamp就可以了
然后更新你的字段值

⑵ sql语句实现考勤报表，sql语句怎样实现员工同一天只有两次考勤

两次考勤：select 员工ID,TRUNC(TIME,'d') FROM 考勤表 group by 员工ID,TRUNC(TIME,'d')

having count(*)=2;
漏打：select 员工ID,TRUNC(TIME,'d') FROM 考勤表 group by 员工ID,TRUNC(TIME,'d')
having count(*)<2;