Count Records where Field is Empty

A rather basic question here.

I'm able to query records from a related table, such as Users who've created a record in a separate table.

Some records will be 'deleted' where I'll be adding a timestamp to those records as shown in the image.

I'd like to ignore these records where there is a timestamp present. Assuming this is good practice - happy to hear suggestions.

Any help is appreciated![Screen Shot 2021-11-13 at 8.36.02 PM.png]