How to store NULL values in datetime fields in MySQL?

Question

I have a \"bill_date\" field that I want to be blank (NULL) until it\'s been billed, at which point the date will be entered.

I see that MySQL does not like NULL val

Answer 1

I just discovered that MySQL will take null provided the default for the field is null and I write specific if statements and leave off the quotes. This works for update as well.

if(empty($odate) AND empty($ddate))
{
  $query2="UPDATE items SET odate=null, ddate=null, istatus='$istatus' WHERE id='$id' ";
};