Have you noticed that in SharePoint, there is no obvious way to join two lists or libraries, using a common field? For those of you who have ever used Microsoft Access or any other database, you know that you can just create queries to display joined tables. In this screencast, I show an example of how you can show data from 2 different lists, as ONE.
There is a contact list of vendors on your site, and there is a list of appointments that you have with those vendors. You want to display a list of upcoming appointments, and also display that associated vendor's phone number in the appointment list. Here's how!
There are so many uses for this "Join" functionality! Another example that I've used at work (in healthcare) is a list of all of the room numbers in the hospital, with the phone number for each room. This is a static list. There is also a list of patient appointments, and each patient has an associated room number. NOW, I can display the list of patient appointments, and also include that room's phone number along with the patient... data from two different lists!
Join View of SharePoint Lists