>>
>>There's no difference but I prefer NULL because it's the same in MS SQL Server.
>>The same goes for OR AND NOT
>
>Thank you, Sergey. I have pretty much stopped using OR/AND with periods a long time ago but for some reason continued using .NULL. with dots. So now I will save two keystrokes on every entry.

There's one exception I forgot to mention. In the Properties sheet .NULL. should be used because NULL will be treated as a string value. Or you can use =NULL .