我们知道MySQL中TIME字段的范围是‘-838:59:59’到‘838:59:59’。现在，如果 TIMEDIFF() 函数的输出超出此范围，则 MySQL 将返回 \'-838:59:59\' 或 \'838:59:59\'，具体取决于参数的值。
示例
mysql> Select TIMEDIFF(\'2017-09-01 03:05:45\',\'2017-10-22 03:05:45\')AS \'Out of Range TIME Difference\'; +------------------------------+ | Out of Range TIME Difference | +------------------------------+ | -838:59:59 | +------------------------------+ 1 row in set, 1 warning (0.00 sec) mysql> Select TIMEDIFF(\'2017-10-22 04:05:45\',\'2017-09-01 03:05:45\')AS \'Out of Range TIME Difference\'; +------------------------------+ | Out of Range TIME Difference | +------------------------------+ | 838:59:59 | +------------------------------+ 1 row in set, 1 warning (0.01 sec)
