We have the following code where we perform a table lookup using set statement with key = option.   *master table; data ftr; trnid = 'trade1'; trnidsce = 'a'; issueid = ''; issueidsce = ''; rcvudlyid = 'ABC'; rcvudlyidsce = '2'; run; *lookup table; data ins (index = (issueKey = (issueid issueidsce) / unique)) ; issueid = 'ABC'; issueidsce = '2';  ciultarlvcflg = 'Y'; run; *final table; data final;  set ftr;   set ins2 (keep = issueid issueidsce ciultarlvcflg             rename = (issueid = rcvudlyid                      issueidsce = rcvudlyidsce)) key = issueKey / unique;   if _iorc_ then _error_ = 0; run; As I understand the key = option should do the lookup via definition of issueKey, i.e. if issueid and issueidsce is matching between ins2 and ftr dataset. However it seems the lookup is happening by rcvudlyid rcvudlyidsce after the rename and I am now able to get value of ciultarlvcflg. I was expecting it to throw an error given the original variables used to create the index was renamed. Can someone help me to understand what is happening? Many thanks.       ... View more