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Chapter 10. Understanding Jet Operators ... > In the Real World—The Algebra of Acc...

In the Real World—The Algebra of Access Expressions

A junior high school algebra class provides most students their first introduction to abstract mathematics. Expressions (algebraic formulas) are crucial to the majority of decision-support queries you design, as well as presentation of calculated data in form and report text boxes and other text-based controls. The colon following the column name of a calculated expression is the equivalent of an equal sign; in mathematical terms, Amount:CCur([UnitPrice]*[Quantity]*(1[Discount])) is the equivalent of curAmount=CCur(sngUnitPrice*intQuantity*(1-sngDiscount)) in VBA.

Similarly, functions that convert data types and format query columns also are important to forms and reports. The classic definition of a function is this: If when X is given, Y is determined, then Y is a function of X. For example, in Price:Format([UnitPrice], "#,##0.00"), the value of the UnitPrice field (X) uniquely determines the value of the calculated Price (Y) column. The fact that queries can have calculated and specially formatted columns is one of the reasons this book uses the term column with queries and field for tables.


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