MySQL microsecond()函數
MICROSECOND(expr)
返回時間或日期時間表達式expr的微秒，這個數字範圍為 0 到 999999。
mysql> SELECT MICROSECOND('12:00:00.123456');
+---------------------------------------------------------+
| MICROSECOND('12:00:00.123456') |
+---------------------------------------------------------+
| 123456 |
+---------------------------------------------------------+
1 row in set (0.00 sec)
