There are some things that a subquery alone can't manage, and there are some times when it suits us better to perform cross-referencing on the client side. Subqueries for example, are very good for excluding and narrowing down results, but they don't really help by providing any further information about the results or many clues to common similarities.

In this recipe we're going to make two FQL requests: one to retrieve information about the current user's friends, and another to retrieve information about users that are tagged in photos alongside the current user—the same FQL queries as we used in our earlier recipe Using logical operators in FQL requests.

In our previous recipe, we combined these two separate queries as subqueries, grouping together the results of both queries into a single set of results. In this recipe we want to be able to distinguish between the results of each query, and identify results that don't overlap in the...