How to pad a number with leading zero in a SAS Macro loop counter?

Question

So I have a range of datasets in a specific library. These datasets are named in the format DATASET_YYYYMM, with one dataset for each month. I am trying to append a range of these datasets based on user input for the date range. i.e. If start_date is 01NOV2019 and the end_date is 31JAN2020, I want to append the three datasets: LIBRARY.DATASET_201911, LIBRARY.DATASET_201912 and LIBRARY.DATASET_202001.

The range is obviously variable, so I can't simply name the datasets manually in a set function. Since I need to loop through the years and months in the date range, I believe a macro is the best way to do this. I'm using a loop within the SET statement to append all the datasets. I have copied my example code below. It does work in theory. But in practice, only if we are looping over the months of November and December. As the format of the dataset name has a two digit month, for Jan-Sept it will be 01-09. The month function returns 1-9 however, and of course a 'File DATASET_NAME does not exist' error is thrown. Problem is I cannot figure out a way to get it to interpret the month with leading 0, without ruining functionality of another part of the loop/macro.

I have tried numerous approaches to format the number as z2, cannot get any to work. i.e. Including PUTN functions in the DO line for quote_month as follows, it ignores the leading zero when generating the dataset name in the line below.

%DO quote_month = %SYSFUNC(IFN(&quote_year. = &start_year.,%SYSFUNC(PUTN(&start_month.,z2.)),1,.)) %TO %SYSFUNC(IFN(&quote_year. = &end_year.,%SYSFUNC(PUTN(&end_month.,z2.)),12,.));

Below is example code (without any attempt to reformat it to z2) - it will throw an error because it cannot find 'dataset_20201' because it is actually called 'dataset_202001'. The dataset called dataset_combined_example produces the desired output of the code by manually referencing the dataset names which it will be unable to do in practice. Does anyone know how to go about this?

DATA _NULL_;
    FORMAT start_date end_date DATE9.;
    start_date = '01NOV2019'd;
    end_date = '31JAN2020'd;
    CALL symput('start_date',start_date);
    CALL symput('end_date',end_date);
RUN;

DATA dataset_201911;
   input name $;
   datalines;
Nov1
Nov2
;
RUN;
DATA dataset_201912;
   input name $;
   datalines;
Dec1
Dec2
;
RUN;
DATA dataset_202001;
   input name $;
   datalines;
Jan1
Jan2
;
RUN;

DATA dataset_combined_example;
    SET dataset_201911 dataset_201912 dataset_202001;
RUN;


%MACRO get_table(start_date, end_date);
    %LET start_year = %SYSFUNC(year(&start_date.));
    %LET end_year = %SYSFUNC(year(&end_date.));
    %LET start_month = %SYSFUNC(month(&start_date.));
    %LET end_month = %SYSFUNC(month(&end_date.));
    DATA dataset_combined;
        SET
            %DO quote_year = &start_year. %TO &end_year.;
                %DO quote_month = %SYSFUNC(IFN(&quote_year. = &start_year.,&start_month.,1,.)) %TO %SYSFUNC(IFN(&quote_year. = &end_year.,&end_month.,12,.));
                    dataset_&quote_year.&quote_month.
                %END;
            %END;
        ;
    RUN;
%MEND;
%get_table(&start_date.,&end_date.);

Answer 1

You could do this using putn and z2. format.

%DO quote_year = &start_year. %TO &end_year.;
     %DO quote_month = %SYSFUNC(IFN(&quote_year. = &start_year.,&start_month.,1,.)) %TO %SYSFUNC(IFN(&quote_year. = &end_year.,&end_month.,12,.));
            dataset_&quote_year.%sysfunc(putn(&quote_month.,z2.))
     %END;
%END;