copytruncate – Copy the log file and then empties it. This makes sure that the log file Rails is writing to always exists so you won’t get problems because the file does not actually change. If you don’t use this, you would need to restart your Rails application each time.
mysql> select id from buildings where created_at = '0000-00-00 00:00:00';
created_atが '0000-00-00 00:00:00'になっているデータがヒットする。
mysql> UPDATE buildings set created_at = '2004-01-29 00:00:00'where id in (select id from buildings where created_at = '0000-00-00 00:00:00');
ERROR 1292 (22007): Incorrect datetime value: '0000-00-00 00:00:00'forcolumn'created_at' at row1