django blank 和autonow

    Blank = True # null = True ADMIN user submits the form is empty, save to database or NULL 
    # Black - False indicates that the user front-end form is submitted can not be empty, verify 


    # disdain auto_now will have a front-end time and space, auto- the -now = Ture was a changing of 
    the time #auto_now_add created just add one time, subsequent edits will not change the time 
    # summary auto_now been following the system time is changed, the 
    # auto_now_add just in time to add a plus one time, after it does not change, allocation of time suitable for such a field