mysql timestamp型<=>datetime型に変換

datetime型をtimestampに変換

select unix_timestamp('2017-10-24 09:31:42');
-> 1508805102

 timestampをdatetime型に変換

select from_unixtime(1508805102);
-> 2017-10-24 09:31:42

select from_unixtime(1508805102, '%Y/%m/%d %H:%i:%s');
->  2017/10/24 09:31:42