created_at datetime default now()

created_at-and-updated_at.sql

# If you need to add a created_at field in your database
# that inserts "now()" when the insert statement is run, you
# can use the following script.
# It uses timestamps, but removes the "on update" for the
# created_at column, but keeps it on the updated_at (which
# needs to update at every change).
#
# got this snippet here:
# http://bugs.mysql.com/bug.php?id=27645
# (search for: "[7 Oct 2009 4:25] Diego Medina")

created_at timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
updated_at timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP