SELECT TIMESTAMPDIFF

SELECT TIMESTAMPDIFF函数是用来计算两个日期或时间之间的差值的函数。它的语法是：SELECT TIMESTAMPDIFF(unit, start_datetime, end_datetime)。其中unit是计算的单位，start_datetime和end_datetime是要计算的两个日期或时间。函数会返回两个日期或时间之间相差的单位数。

在给定的引用中，功能示例如下：

SELECT TIMESTAMPDIFF(FRAC_SECOND,'2012-10-01','2013-01-13'); # 返回毫秒数
SELECT TIMESTAMPDIFF(SECOND,'2012-10-01','2013-01-13'); # 返回秒数
SELECT TIMESTAMPDIFF(MINUTE,'2012-10-01','2013-01-13'); # 返回分钟数
SELECT TIMESTAMPDIFF(HOUR,'2012-10-01','2013-01-13'); # 返回小时数
SELECT TIMESTAMPDIFF(DAY,'2012-10-01','2013-01-13'); # 返回天数
SELECT TIMESTAMPDIFF(WEEK,'2012-10-01','2013-01-13'); # 返回星期数
SELECT TIMESTAMPDIFF(MONTH,'2012-10-01','2013-01-13'); # 返回月数
SELECT TIMESTAMPDIFF(QUARTER,'2012-10-01','2013-01-13'); # 返回季度数
SELECT TIMESTAMPDIFF(YEAR,'2012-10-01','2013-01-13'); # 返回年数