`last_login` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP

`created` datetime NOT NULL DEFAULT '0000-00-00 00:00:00'

unsigned/true : to generate "UNSIGNED" in the field definition.
default/value : to generate a default value in the field definition.
null/true : to generate "NULL" in the field definition. Without this, the field will >     default to "NOT NULL".
auto_increment/true : generates an auto_increment flag on the field. Note that the >     field type must be a type that supports this,
such as integer