要把学生作业表中的完成时间,更新到作业历史表的完成时间上,涉及到两个表的update操作,两个表的信息如下:
学生作业表:homework_student
作业历史表:user_homework_exampaper_history
方法一:
update user_homework_exampaper_history t2 set complete_time =
(select complete_time from homework_student where user_id=t2.user_id and homework_id=t2.homework_id )
方法二:
update homework_student t1 ,user_homework_exampaper_history t2 set t1.complete_time=t2.complete_time
where t1.user_id = t2.user_id and t1.homework_id = t2.homework_id