Hi All I have an interview question to get an answer for. The only condition is we are not to use merging for the following and to do it with the help of macros only. Question: There are two datasets. One is having Subject and visit, other is having visit only. data t; input subject visit @@; datalines ; 001 1 001 2 001 3 001 8 002 1 002 8 ; data r; input  visit @@; datalines ; 1 2 3 4 5 6 7 8 ; I want another dataset which will compare the visit from first dataset to the second dataset and will give the missing visits in new variable, one observation for each missing visit for each subject. Following is the example of final output required: subject visit missingvisit 001      1 001      2 001      3      001            4 001            5 001            6 001            7 001      8 Reminder - not to use the merging Thanks everyone ... View more