MySQL DATEDIFF TIMEDIFF

DATEDIFF 只计算到天的单位

TIMEDIFF 精确到毫秒单位

mysql> SELECT DATEDIFF (
    ->     '2000-01-01 00:00:00.000000',
    ->     '2000-01-02 05:06:07.000008') A;
+------+
| A    |
+------+
|   -1 |
+------+
1 row in set (0.00 sec)

mysql> SELECT
    ->   TIMEDIFF ('2000-01-01 00:00:00.000000',
    ->             '2000-01-02 05:06:07.000008') A;
+------------------+
| A                |
+------------------+
| -29:06:07.000008 |
+------------------+
1 row in set (0.00 sec)

如果 要以秒为单位返回，使用 TIME_TO_SEC 函数：

mysql> SELECT
    ->   TIME_TO_SEC(
    ->     TIMEDIFF ('2000-01-01 00:00:00.000000',
    ->              '2000-01-02 05:06:07.000008')) A;
+---------+
| A       |
+---------+
| -104767 |
+---------+
1 row in set (0.03 sec)