题解 | #删除记录（二）#
删除记录（二）
http://www.nowcoder.com/practice/964c9f7fffbb4ab18b507cfed4111b4a
delete from exam_record
where submit_time is null
#sql中使用timestampdiff函数获取时间差
or timestampdiff(minute,start_time,submit_time)<5
order by start_time
limit 3;
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