mysql-est timestamp

i've browsed the archive and see that there is a way in using triggers to
achieve automatic modification time stamp. i'm porting a mysql
application, and need that same functiona. pgsql's timestamp is for
date+time[+zone]. however, for mysql it's used to stamp the time when the
record was inserted or updated.

regarding the trigger, can someone explain how this works? i looked at the
code provided in the archive and was quite lost. my other concern is i
still have to write the query in such a way so that it'll work in the
other DB's as well. considering the dramatic differences in implementation
of timestamp and what they mean, is there a cleaner way to do it besides
"if (thisDB) / elseif (thatDB) .." block in the client language?