Help regarding if-else

Let me describe what I want to implement.
There are two columns, say 'D' & 'E'; each can take either of the two values 0 or 1. Now, in a third column, say 'G', I want to see results based on the product of values of the two columns D & E. If the product is a 1, I want to see the output as 'YES' and if the product is a 0, I want to see a 'NO'. I have figured out how to do it: =IF(D4*E4=1, "YES", IF(D4*E4=0, "NO", "")). My thought behind using the nested if is that the cell would remain blank if there are no vales input in the cells of D & E. But sadly, it's not happening. When I apply the given if-condition to a range of cells in the column G, all the cells take a default output of "NO".
How can I get what I want? If the output value is 0, then NO; if it's 1, then a yes, and if no values are input yet, I want them to remain blank.

Try

=IF(OR(D4="",E4=""),"",IF(D4*E4,"Yes","NO"))

It's working.
Thanks a ton.
But can you tell me how did that piece of code work?

=IF(OR(D4="",E4=""),"",IF(D4*E4,"Yes","No"))

The OR tests if either D4 or E4 is blank and result is blank

the IF test returns TRUE condition if D4*E4 is 1 (any value other than 0 will return TRUE) , so results is "Yes", otherwise "No"

The formula below is the equivalent .....

=IF(OR(D4="",E4=""),"",IF(D4*E4=1,"Yes","No"))