MySQLのCREATE TABLEの挙動

foo.sql

mysql> select version();
+-----------+
| version() |
+-----------+
| 5.6.27    |
+-----------+
1 row in set (0.00 sec)

mysql> create table a(
    -> a timestamp not null comment 'foo',
    -> b timestamp not null comment 'bar'
    -> );
Query OK, 0 rows affected (0.03 sec)

mysql> desc a;
+-------+-----------+------+-----+---------------------+-----------------------------+
| Field | Type      | Null | Key | Default             | Extra                       |
+-------+-----------+------+-----+---------------------+-----------------------------+
| a     | timestamp | NO   |     | CURRENT_TIMESTAMP   | on update CURRENT_TIMESTAMP |
| b     | timestamp | NO   |     | 0000-00-00 00:00:00 |                             |
+-------+-----------+------+-----+---------------------+-----------------------------+
2 rows in set (0.01 sec)