Had a question about performance today and I'm not sure what the best way to attack the problem is. We have 2 tables where we can perform a left outer join to get the data set we need. Is it better to do this left outer join or is it better to do get 2 different data sets then do a nested loop to find the matching entries? I know nested, linear search loops are big O (n^2) but doesn't a left outer join have to do the same thing?? So which one would be faster and why??