mysql >select sec_to_time(time_to_sec(cast('16:32:18' as time)));
+----------------------------------------------------+
| sec_to_time(time_to_sec(CAST('16:32:18' AS TIME))) |
+----------------------------------------------------+
| 16:32:18 |
+----------------------------------------------------+
1 row in set (0.53 sec)
mysql [test]>select sec_to_time(59538);
+--------------------+
| sec_to_time(59538) |
+--------------------+
| 16:32:18 |
+--------------------+
1 row in set (0.03 sec)