题解 | #插入记录（二）#

insert into exam_record_before_2021(uid, exam_id, start_time, submit_time, score)
select uid, exam_id, start_time, submit_time, score
from exam_record where YEAR(submit_time) < '2021'

1.如果需要避开某些字段，最好采用指定字段插入。比如这题中要避开id字段，否则新表的id就不连续了
2.判断是否为null是 is/is not，而不是 !=
3.datetime数据的比较，可以用内置函数YEAR()来过滤时间范围