Facebook multiquery

Evaluates a series of FQL (Facebook Query Language) queries in one call and returns the data at one time.

This method takes a JSON-encoded dictionary called queries where the individual queries use the exact same syntax as a query made with fql.query. However, this method allows for more complex queries to be made. You can fetch data from one query and use it in another query within the same call. The WHERE clause is optional in the latter query, since it references data that’s already been fetched. To reference the results of one query in another query within the same call, specify its name in the FROM clause, preceded by #.

For example, say you want to get some data about a user attending an event. Normally, you’d have to perform two queries in a row, waiting for the results of the first query before running the second query, since the second query depends on data from the first one. But with fql.multiquery, you can run them at the same time, and get all the results you need, giving you better performance than running a series of fql.query calls. First, you need to get the user ID and RSVP status of each attendee, so you’d formulate the first query – query1 – like this:

"query1":"SELECT uid, rsvp_status FROM event_member WHERE eid=12345678"

Then to get each attendee’s profile data (name, URL, and picture in this instance), you’d make a second query – query2 – which references the results from query1. You formulate query2 like this:

"query2":"SELECT name, url, pic FROM profile WHERE id IN (SELECT uid FROM #query1)"

This method also has better performance than running a series of fql.query calls with batch.run.

For more information about fql.multiquery see this link where these texts are taken from.