SAS count and summarize if conditions on variables are true - sas

Question

I have a data set with 3 columns: Name, System, UserID. I want to count how many times an individual appears in the report, but not count them if they're different people with the same name. Distinction is made by the UserID field and only within a single system. If a single name has multiple lines with the same system and different User ID, then all the observations with that name would be marked for review. For this data set, I would want to see the output below.
Name System UserID
John Doe Sys1 [blank]
John Doe Sys1 AB1234
John Doe Sys2 AB2345
Jane Doe Sys1 AA2345
Jane Doe Sys1 AA23456
Jane Doe Sys2 AA2345
Joe Smith Sys1 JS963
Joe Smith Sys2 JS741
Name Count System Follow-up
John Doe 1 Sys1 - Yes
John Doe 1 Sys1 - AB1234 Yes
John Doe 1 Sys2 - AB2345 Yes
Jane Doe 1 Sys1 - AA2345 Yes
Jane Doe 1 Sys1 - AA23456 Yes
Jane Doe 1 Sys2 - AA2345 Yes
Joe Smith 2 Sys1 - JS963, Sys2 - JS741 No
Any help would be greatly appreciated!
The code I have is below. It's currently just doing a count of names in general and don't know how to add the conditions.
PROC SQL;
CREATE TABLE Sorted_Master_Original AS
SELECT Name,
COUNT(Name) AS Total,
System,
UserID,
CATX(' - ',System,UserID) AS SystemID
FROM Master_Original
WHERE Name <> ""
GROUP BY Name;
QUIT;
DATA TESTDATA.Final_Listing;
LENGTH SystemsAccessed $200.;
DO UNTIL (last.Name);
SET Sorted_Master_Original;
BY Name NOTSORTED;
SystemsAccessed=CATX(', ',SystemsAccessed,SystemID);
END;
DROP System SystemID;
RUN;

Answer 1

The case of determining a signal over a group, and then applying to each member in the group can be accomplished using two DOW loops in sequence. The first is as you have coded with a last. loop test and the set and by within the loop, and the second will be for reiterating the group via a like sized loop over the group in separate SET buffer -- at which time the signal can be applied.
Data
data have;
length Name System UserID $20;
input Name & System & UserID; datalines;
John Doe Sys1 .
John Doe Sys1 AB1234
John Doe Sys2 AB2345
Jane Doe Sys1 AA2345
Jane Doe Sys1 AA23456
Jane Doe Sys2 AA2345
Joe Smith Sys1 JS963
Joe Smith Sys2 JS741
Bob Smith Sys3 MS13
run;
Order for by group processing
proc sort data=have;
by Name System UserId;
run;
DATA Step with sequential DOW loops
data want(keep=name count system_userid_list followup);
* loop over name group;
do _n_ = 1 by 1 until (last.name);
set have;
by name system userid;
* tests of conditions within the group determine some signal;
* check if there is more than one userid within a system within the name group;
if not (first.system and last.system) then
count = 1;
end;
if not count then count = _n_;
length system_userid_list $200;
followup = ifc(count=1 and _n_>1 ,'Yes','No');
* followup 'signal' will be applied/available to each row of the group;
* either output single row as followup, or concat to an aggregate list;
* mixed output of singles and aggregates, good idea?;
* reiterate over group in second SET buffer;
do _n_ = 1 to _n_;
set have;
item = catx(' - ',system,userid);
if count > 1 then
system_userid_list = catx(',',system_userid_list,item);
else do;
system_userid_list = item;
output;
end;
end;
if count > 1 then output;
run;