You would need two steps: proc sort data=lib.result; by id cam date; run; data want; set lib.result; by id; if first.id and cam=1; run; Note, I have only done this based on the test data you provided (and provided not in a datastep!!).  Would need to see some actual descriptive test data in the form of a datastep and what you want to see out at the end. ... View more

@gsaba wrote: now i wrote this:    %macro appending (startmonth, endmonth); data file1; input(gsaba.products_2018_01, date9.); run; data file2; input(gsaba.products_2018_02, date9.); run; data file3; input(gsaba.products_2018_03, date9.); run; data file4; input(gsaba.products_2018_04, date9.); run; data file5; input(gsaba.products_2018_05, date9.); run; data appendedtables; set %do 'i'=&startmonth %to &endmonth; file&'i' %end; run; %mend; %appending (startmonth = 1, endmonth = 5);   but it doesn't work 😞 Well, the advice was to get this to work in one situation, one iteration of the loop, without macros. The code you show above still uses macros, which I have highlighted in red. So you are not yet at the situation that we are asking you to achieve, that is WORKING code WITHOUT macros. ... View more