Jika Anda ragu, sintaksnya dijelaskan di sinihttp://dev.mysql.com/doc/refman/5.5/en/alter-table.html
ALTER TABLE yourTable
ADD COLUMN new_date DATETIME NOT NULL DEFAULT 20110126143000 AFTER preceding_col
atau
ALTER TABLE yourTable
ADD COLUMN new_date DATETIME NOT NULL DEFAULT '2011-01-26 14:30:00' AFTER preceding_col
(Saya lebih suka format DATETIME numerik)