Not sure why I had it in my head that INTCK was being used, YRDIF doesn't have the ACTUAL parameter so that needs to be fixed. It will still return an error because DOB is not in the input data set. Note that the KEEP on the SET statement does not include DOB.    set emp (keep=Manager_EMP_ID Employee_ID Salary); Then if you look at the data set option closely, it's a DROP. So you know have:   manager_emp_id employee_id salary and AGE/DOB (all missing), and then you drop more variables:   data emp(drop=Manager_EMP_ID Salary); So in the end, you end up with: employee_id, age and DOB, with only Employee_ID filled in.    This is a really, really bad example IMO. You should try finding a different method of studying, I recommend the Little SAS book which has been edited and used by hundred if not thousands of SAS programmers.              ... View more

@Masande wrote: If I understand it correctly, the variables i and j are coming from a different data set and their values are retained. sum(i,j) is newly created, hence its value is set to missing. Is that what I'm supposed to see? I and J are variables being read from a dataset.  So they are retained, but in a normal simple data step where the SET statement is the first thing that execute is really doesn't matter whether they are "retained" or not since whatever value they had is immediately changed by executing the SET statement.   SUM(I,J) is a function call and so has nothing to do with the point of the question.  The difference between the two steps is that in one the value is being assigned on a variable that is coming from an input dataset and in the other it is being assigned to a variable that is NOT coming from an input dataset.  So in one the value BEFORE the set statement reflects the value at the end of the previous iteration. And in the other the value is missing before the assignment statement gives it a value.   In the simple data step generated by PROC IMPORT none of the variables are coming from an input dataset, so none of them are "retained".  Also since each iteration of the data step includes in INPUT statement that sets the values of the variables it doesn't really matter whether the variables are retained.   That is why it seems strange to mention this issue in the context of PROC IMPORT.   ... View more

Put all files with identical structure (and only those)in a directory, and use wildcards to read all files in one step. Use the filename= option to retrieve the name of the currently read file. ... View more