Hi everyone,    I'm brand new to SAS, so please bear with me if I'm missing something obvious. I've got two datasets, each with patient data, and I need to identify discrepancies between them. The first dataset is structured horizontally, starting with a unique patient ID, and a list of dates corresponding to clinic visits. This is the "gold standard" dataset. There's one row per ID:  Patient_ID      Date1          Date2            24          12/2/15      12/23/15               25          12/2/15      12/23/15         The other dataset is structured vertically, and contains information on whether or not forms were filled out at each visit. Each Patient_ID is listed multiple times to denote multiple visits. The "Date of Visit" variable values should correspond to values in the "Date" variables in the first dataset, but I've been told that this latter dataset may have extra or missing entries compared to the first.  Patient_ID      Date of Visit         Form1      Form2     Form3           24                12/2/15              Yes           No            Yes                  24                12/23/15            Yes           Yes           Yes        25                12/2/15              Yes           No            Yes       25                12/23/15            Yes           Yes           Yes            My first thought was to try to merge the datasets in such a way that I could create an indicator variable to identify instances where date of visit did not = corresponding date from dataset one, but honestly, I can't quite wrap my head around how to structure the merged dataset in such a way that it retains all the necessary data.    Any ideas would be greatly appreciated, thank you! ... View more