@cristoban wrote: Well for the first one, the proc sql code, which is the one I am most concerned with, I had said it created a new dataset  taking variables A and B from datasets     It's taking variables VA and VB, the A and B are table alias to indicate which is the source table, so that is incorrect.    @cristoban wrote:  its left join which takes everything from A, even if there is nothing from B.   This part is mostly correct, any records with an ID in A is kept, so your output data set size should be >= size of data set A, assuming no WHERE statements.   Where my confusion came is the on strip clause. I mentioned strip removing leading/trailing zeros blanks, so by guess was that it would produce a dataset where there was matches anywhere in dataset A and B regardless of blanks or zeros. But I am, not sure this is correct  STRIP() only affects leading spaces, not zeroes, so that portion is incorrect. ... View more