或者，您可以使用TIMEDIFF函数

mysql> SELECT TIMEDIFF('2000:01:01 00:00:00', '2000:01:01 00:00:00.000001');
'-00:00:00.000001'
mysql> SELECT TIMEDIFF('2008-12-31 23:59:59.000001' , '2008-12-30 01:01:01.000002');
 '46:58:57.999999'

该函数获取两个日期的差值，并以日期格式yyyy-mm-dd显示。您只需要执行下面的代码，然后使用该函数。执行后，您可以像这样使用它

SELECT datedifference(date1, date2)
FROM ....
.
.
.
.


DELIMITER $$

CREATE FUNCTION datedifference(date1 DATE, date2 DATE) RETURNS DATE
NO SQL

BEGIN
    DECLARE dif DATE;
    IF DATEDIFF(date1, DATE(CONCAT(YEAR(date1),'-', MONTH(date1), '-', DAY(date2)))) < 0    THEN
                SET dif=DATE_FORMAT(
                                        CONCAT(
                                            PERIOD_DIFF(date_format(date1, '%y%m'),date_format(date2, '%y%m'))DIV 12 , 
                                            '-',
                                            PERIOD_DIFF(date_format(date1, '%y%m'),date_format(date2, '%y%m'))% 12 , 
                                            '-',
                                            DATEDIFF(date1, DATE(CONCAT(YEAR(date1),'-', MONTH(DATE_SUB(date1, INTERVAL 1 MONTH)), '-', DAY(date2))))),
                                        '%Y-%m-%d');
    ELSEIF DATEDIFF(date1, DATE(CONCAT(YEAR(date1),'-', MONTH(date1), '-', DAY(date2)))) < DAY(LAST_DAY(DATE_SUB(date1, INTERVAL 1 MONTH))) THEN
                SET dif=DATE_FORMAT(
                                        CONCAT(
                                            PERIOD_DIFF(date_format(date1, '%y%m'),date_format(date2, '%y%m'))DIV 12 , 
                                            '-',
                                            PERIOD_DIFF(date_format(date1, '%y%m'),date_format(date2, '%y%m'))% 12 , 
                                            '-',
                                            DATEDIFF(date1, DATE(CONCAT(YEAR(date1),'-', MONTH(date1), '-', DAY(date2))))),
                                        '%Y-%m-%d');
    ELSE
                SET dif=DATE_FORMAT(
                                        CONCAT(
                                            PERIOD_DIFF(date_format(date1, '%y%m'),date_format(date2, '%y%m'))DIV 12 , 
                                            '-',
                                            PERIOD_DIFF(date_format(date1, '%y%m'),date_format(date2, '%y%m'))% 12 , 
                                            '-',
                                            DATEDIFF(date1, DATE(CONCAT(YEAR(date1),'-', MONTH(date1), '-', DAY(date2))))),
                                        '%Y-%m-%d');
    END IF;

RETURN dif;
END $$
DELIMITER;

select 
unix_timestamp('2007-12-30 00:00:00') - 
unix_timestamp('2007-11-30 00:00:00');

SELECT TIMEDIFF('2007-12-31 10:02:00','2007-12-30 12:01:01');
-- result: 22:00:59, the difference in HH:MM:SS format


SELECT TIMESTAMPDIFF(SECOND,'2007-12-30 12:01:01','2007-12-31 10:02:00'); 
-- result: 79259  the difference in seconds

因此，您可以使用TIMESTAMPDIFF来实现您的目的。

为什么不干脆

从表中选择Sum(Date1 - Date2)

Date1和date2是datetime

SELECT TIMESTAMPDIFF(SECOND,'2018-01-19 14:17:15','2018-01-20 14:17:15');

第二种方法

选择(DATEDIFF(1993-02-20)、1993-02-19)

CURRENT_TIME() --this will return current Date
DATEDIFF('','') --this function will return  DAYS and in 1 day there are 24hh 60mm 60sec