Comments - UNIX_TIMESTAMP

select from a table is still 0

select request_time  from exec_log where id=11391900003;
+---------------------+
| request_time        |
+---------------------+
| 0000-00-00 00:00:00 |
+---------------------+
select UNIX_TIMESTAMP(request_time)  from exec_log where id=11391900003;
+------------------------------+
| UNIX_TIMESTAMP(request_time) |
+------------------------------+
|                            0 |
+------------------------------+


| exec_log | CREATE TABLE `exec_log` (
  `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  `client_ip` int(10) unsigned NOT NULL,
  `request_time` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  `status` int(10) unsigned NOT NULL DEFAULT '0',
  `succ_count` int(10) unsigned NOT NULL DEFAULT '0',
  `first_touch_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`),
  KEY `client_ip` (`client_ip`),
  KEY `succ_count_btree` (`succ_count`) USING BTREE,
  KEY `first_touch_time_tree` (`first_touch_time`) USING BTREE
) ENGINE=InnoDB AUTO_INCREMENT=11391900004 DEFAULT CHARSET=latin1 |

But select from view is NULL.

select last_fetch_time from clients_info_logic where ip='1.1.1.6';
+---------------------+
| last_fetch_time     |
+---------------------+
| 0000-00-00 00:00:00 |
+---------------------+
select UNIX_TIMESTAMP(last_fetch_time) from clients_info_logic where ip='1.1.1.6';
+---------------------------------+
| UNIX_TIMESTAMP(last_fetch_time) |
+---------------------------------+
|                            NULL |
+---------------------------------+