题解 | #删除记录（二）#

delete from exam_record 
WHERE timestampdiff(MINUTE,start_time,submit_time) < 5
OR submit_time is NULL
ORDER BY start_time
LIMIT 3;

时间差：

• TIMESTAMPDIFF(interval, time_start, time_end)可计算time_start-time_end的时间差，单位以指定的interval为准，常用可选： SECOND 秒MINUTE 分钟（返回秒数差除以60的整数部分）HOUR 小时（返回秒数差除以3600的整数部分）DAY 天数（返回秒数差除以3600*24的整数部分）MONTH 月数YEAR 年数

TIMESTAMPDIFF(MINUTE,start_time,end_time)

作答时间最早的三条，先对作答时间进行排序，然后用limit限制前三条

ORDER BY start_time LIMIT 3