Merging three datasets with multiple instances of uniqe identifier

I am attempting to merge three datasets that were passed down to me and I am at a bit of a loss. Two of the datasets contain results for psychological instruments and the third contains basic admission statistics. The final analysis goal for the merged dataset will be to examine the relationships between admission statistics and instrument outcomes. Each of the datasets contains medical record (MR) numbers which is what I plan on using as the uniqe identifer for merge. However, each dataset also contains multiple instances of MR number due to patient re-admission. My questions are as follows:

1. Within a single dataset, is it possible to combine (using syntax or point/click) data for each MR number onto a single row. I would like to do this for each dataset so that I can then merge based upon MR number and combine all information into a single line.

2. Is it possible to merge the three datasets based upon MR number and admission date so that each admission would have its own line. See below for illustration?

Client X, admit date 1, test results for admit date 1, admission info for admit date 1
Client X, admit date 2, test results for admit date 2, admission info for admit date 2

I know I can do some of these things the the painful way by identfying and moving them myself however, I wanted to see if there was a more efficent way to accomplish them.