You don't need to manually do any type of linking. If the fields are named the same in each table, QlikView will automatically link them. If you want to make sure, look at the table viewer (CTRL+T) and you should see that all of your tables are linked by those fields.
Also, if the same fields are used in the tables, QlikView will automatically combine the two tables together so that they become just one table, so for your first two tables, this will most likely be the case.
Yes, I see that they are linked. However, when I try to have 2 axis (by going into Axes > Position and change one to Right(Top)), the graph doesn't render the first expression properly anymore. When the graph from the first expression will have multiple y values per x value, whilst the 2nd expression will be 1 to 1. The table would end up looking something like this:
Date UniqueID Result
8/5/13 100 44
9/5/13 123 55
Here's an attached file with the scenario I outlined. Any help would be appreciated!
test.qvw 151.5 K