Can you provide a more generic descriptive rule instead of just listing an example?
It almost appears appears as if the desired behavior is: when the same STUID has more than one record with the same date that the 'Active Hold'n values are combined.
If this is the case then perhaps:
options validvarname=any;
data sample_data;
infile datalines dlm=',';
input STUID 'Active Holds'n& $21. 'Active Hold Date'n:mmddyy10.;
format 'Active Hold Date'n mmddyy10.;
datalines;
9007741, Flex Advisement, 01/20/2022
9007741, Flex Orientation, 01/20/2022
9008643, Cashier hold, 01/20/2022
9011126, Admissions, 01/07/2022
9013751, Cashier hold, 12/19/2021
9024453, Admissions2, 12/18/2021
;
proc sort data=sample_data;
by stuid 'Active Hold Date'n 'Active Holds'n;
run;
data want;
set sample_data;
by stuid 'Active Hold Date'n 'Active Holds'n;
length holds $ 300;
retain holds;
/* reset the hold variable for the new date*/
if 'first.Active Hold Date'n then call missing(holds);
holds=catx(';',holds,'Active Holds'n );
if 'last.Active Hold Date'n;
drop 'Active Holds'n;
run;
Note that your input is incorrect, no format to read the date, and the Format statement has a different variable.
The sort is partially because the BY statement works much better with sorted data and partially because this way the order of the combined Holds variable will be consistent in order.
The BY allows use of SAS automatic variables First. and Last. to tell if a group starts or ends. Which allows things like resetting or initializing variables or deciding when you are done with a group. Note that when there is a single record in a group it is both the first and last.
The RETAIN keeps a value across iterations of the step. You need an additional variable to do what you request.
The Call Missing sets the value of the variable to missing.
The IF Last is a subsetting IF and records are only written to the output data set when true.
