Seems a fairly basic question but I cannot find how to actually write the query.
For some reason, we have Patients where “system” in “identifier” is not set. Most of identifiers have the system correctly set but system is missing for some of them. I’d like to know how many are in this situation.
I can’t figure out what is search syntax?
This seemed encouraging but I’d like to not restrinct to any value
I’d need something like
Does it exist?