MySQL Tutorial/Date Time Functions/ADDTIME

ADDTIME("01:00:00.999999", "02:00:00.999998");

mysql>
mysql>
mysql>
mysql> SELECT ADDTIME("01:00:00.999999", "02:00:00.999998");
+-----------------------------------------------+
| ADDTIME("01:00:00.999999", "02:00:00.999998") |
+-----------------------------------------------+
| 03:00:01.999997                               |
+-----------------------------------------------+
1 row in set (0.00 sec)
mysql>

ADDTIME(expr1,expr2)

ADDTIME() adds expr2 to expr1 and returns the result.

expr1 is a time or datetime expression, and expr2 is a time expression.

mysql>
mysql> SELECT ADDTIME("1997-12-31 23:59:59.999999","1 1:1:1.000002");
+--------------------------------------------------------+
| ADDTIME("1997-12-31 23:59:59.999999","1 1:1:1.000002") |
+--------------------------------------------------------+
| 1998-01-02 01:01:01.000001                             |
+--------------------------------------------------------+
1 row in set (0.00 sec)
mysql>