mysql时间相减获取秒值

一、mysql时间戳转换

select unix_timestamp();  获取当前时间的时间戳

SELECT FROM_UNIXTIME(1529999834); 时间戳转换为北京时间

要得到正确的时间相减秒值，有以下3种方法：
1、time_to_sec(timediff(t2, t1)),
2、timestampdiff(second, t1, t2),
3、unix_timestamp(t2) -unix_timestamp(t1)

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SELECT AcceptTime,CreateTime, (AcceptTime-CreateTime) sec FROM `req_dlr` WHERE SellOrg="CC经销商88" AND CreateTime>="1527350400" AND CreateTime <= "1529942399" 

AND AcceptTime <>'0' AND makeid = '36000000' AND ReqState <> '97';

此时用第3种方法，时间戳直接相减

3、timediff(time1,time2)，两个时间相减，返回time差值，如图

注意：timediff(time1,time2) 函数的两个参数类型必须相同。

3.1. MySQL （时间和秒互相转换）：time_to_sec(time), sec_to_time(seconds)
select time_to_sec('01:00:05'); -- 3605 转换为秒

select sec_to_time(3605); -- '01:00:05'

3.2、

1、req_dlr表中AcceptTime,CreateTime两个时间戳转换为北京时间，然后只取时间

2、把取到的时间转换为秒，相减后求和

SELECT
sum(time_to_sec(M.A)- TIME_TO_SEC(M.C))
FROM
(
SELECT
date_format(
FROM_UNIXTIME(AcceptTime),
'%H:%i:%S'
) A,
date_format(
FROM_UNIXTIME(CreateTime),
'%H:%i:%S'
) C
FROM
`req_dlr`
WHERE
CreateTime >= "1527350400"
AND CreateTime <= "1529942399"
AND AcceptTime <> '0'
AND makeid = '36000000'
AND ReqState <> '97'
) AS M
WHERE
M.A <= '19:00:00'
AND M.A >= '09:00:00';