题解 | #删除记录（二）#
删除记录（二）
https://www.nowcoder.com/practice/964c9f7fffbb4ab18b507cfed4111b4a
delete from exam_record where submit_time is null or timestampdiff(minute,start_time,submit_time)<5 order by start_time limit 3
该题有两个知识点:
- delete的语法.
- delete的执行顺序
delete的语法:
- 根据条件删除
delete from tb_name where (条件...) order by .. limit...
- 全部删除（表清空，包含自增计数器重置）：
truncate tb_name
delete的执行顺序:from-->where--->order by-->limit-->delete
