One of QBE's most powerful capabilities is that of obtaining summary information almost instantly from specified sets of records in tables. Summarized information from databases is the basis for virtually all management information systems (MIS). Such systems usually answer questions such as, "What are our sales to date for this month?" or "How did last month's sales compare with the same month last year?" To answer these questions, you must create queries that make calculations on field values from all or selected sets of records in a table. To make calculations on table values, you must create a query that uses the table and employs Access's SQL aggregate functions to perform the calculations.