Chapter 8. Queries
"You use a query to answer questions about your database" is a catchy phrase sometimes used in Access training materials. It's helpful as a starting point for discussing queriesbut only as a starting point. As a definition, it leaves out action queries, which don't answer questions but rather change your database. More important, it doesn't embrace the extraordinary breadth of a query's powers, which extend to viewing, integrating, editing, and analyzing data in a multitude of ways. Indeed, it might be more appropriate to ask which Access tasks a query can't do than what it can.
In this chapter, I cover select queries, the most common query and probably what you think of when you hear "query." I begin by discussing some basic but key subjects, such as the various methods for adding all fields of a table to a query, the differences between queries and filters, some simple functions, and similarly useful topics. At about the halfway point, I discuss multitable queries, which is where all the energy you put into designing a relational database begins to pay off. Finally, I introduce Structured Query Language (SQL). The topic is more appropriately the subject of an entire book or series, but you'll get a feel for what it is and see a practical use for it in creating a UNION query.