There are some information I maybe want to say. After reading the first dataset.SAS will set all the variables in PDV missing, So 4 will be missing.and you set it 004. After that, because id is from first dataset ,so it will be retain in PDV (any variable in dataset will be retain ) ,so 5 will not be missing ,it is also 004. I do not know whether it is the reason to make so strange result. Ksharp ... View more