I have two lists (structure undecided), each contains column A and column B. I primarily need to know which elements of column A in list1 are missing in list 2 column A, or which ones in list2 column A are missing from list1 column A. I have no idea where to begin here. Of course a nested loop could achieve it, but there must be some elegant method.

THEN, for those matches where list1colA==list2colA, I also need to know whether or not list1colB==list2colB. I figure once the first question is answered, a single loop can determine this part, but if it can be combined with the above, that would be even better.


so for example, an ID and a timestamp for colA and colB
list 1:
Code:
col A	colB
0	7:35
1	6:03
3	15:07
4	16:58
list2:
Code:
colA	colB
0	7:35
1	8:19
2	3:02
4	16:58
So somehow it would know that colA=colA on 0,1,4, but timestamps are different on 1, and also that list2 has an extra#2 and list1 has an extra#3.

Just a nudge in the right direction is all I need.