I did a quick test, and it looks like TIMESTAMP and BIGINT (14) take up basically the same amount of space. Is that right?
Assuming so, I'm trying to change my USERS table to include a SIGNUPDATE and LASTLOGIN column. Both of these would be TIMESTAMP. I want to set the default to CURRENT_TIMESTAMP, and LASTLOGIN would be "on update CURRENT_TIMESTAMP".
But I get an error that "there can be only one TIMESTAMP column with CURRENT_TIMESTAMP in DEFAULT or ON UPDATE clause".
So how would you guys do this? Just set the default for SIGNUPDATE to "0000-00-00 00:00:00"?
In retrospect, I'm not even sure if I need the "on update" clause at all; if I'm updating it, anyway, then I can just send "CURRENT_TIMESTAMP" with the query. So maybe I should just make the default for both "0000-00-00 00:00:00"?