oracle

create_time:   "CREATE_TIME" DATE DEFAULT SYSDATE,

update_time:  需要用到触发器，

CREATE OR REPLACE TRIGGER TABLE_NAME_TG

BEFORE INSERT OR UPDATE ON TABLE_NAME FOR EACH ROW

BEGIN

    SELECT sysdate INTO:NEW.UPDATE_TIME FROM DUAL;

END;

MySql

自动初始化和更新: (update_time)

DEFAULT CURRENT_TIMESTAMP ON UPDATECURRENT_TIMESTAMP

只自动初始化: (create_time)

DEFAULT CURRENT_TIMESTAMP

只自动更新:

DEFAULT 0 ON UPDATE CURRENT_TIMESTAMP