-- 考察timestampdiff()函数用法:TIMESTAMPDIFF() 函数返回两个日期时间之间的时间间隔。 -- TIMESTAMPDIFF(unit, datetime1, datetime2) -- unit -- 必需的。时间间隔的单位,可用值有: MICROSECOND, SECOND, MINUTE, HOUR, DAY, WEEK, MONTH, QUARTER, YEAR. select c.course_name, round(avg(timestampdiff(MINUTE, in_datetime, out_datetime)), 2) as ...