I had two spreadsheets, one with email address and a couple of values. The other had email address and several more values. I wanted to link the two spreadsheets based on the unique email address, and copy items from one table to the other. I used Mac Numbers and entered the tables as two sheets. I used the Lookup function. In one table I created a new column. In that column cell I entered “=Lookup”, then clicked on the email address in that table, then clicked on the column in the second table where email addresses were located, then clicked on the column where zip codes were located (or other values I wanted to transfer). Then hit return and the values were transferred.
Lookup – Search for, Search where, Results.