Are there examples of expressions in Microsoft Access?

Answer 1

They are like formulas that can be built into Access, often on a form or a query in order to calculate something. In general in databases, anything that can be calculated from other data should not be in a field. For example, if you have the date of birth stored in a field then you should never have the age stored. The age can always be calculated from the date of birth and be accurate at all times. An age changes every year, but the date of birth never does. You would do that calculation by using an expression. If you have the amount of hours worked and the rate of pay, then you can calculate the actual wage at any time, so that does not need to be stored either, and it can be calculated through an expression. So expressions are very useful for doing things in Access.

Answer 2

Say you have two fields - Hours, for the number of hours worked and Rate, for the rate per hour and you want to add a calculated field called Charge to a query so that you could calculate how much to charge for a particular job. The following expression would name the field and also calculate the fee to be charged.

Charge: IIf([Hours]>0,[Hours]*[Rate],0)

Note that the calculated field name is followed by a colon and that the names of existing fields are enclosed in square brackets.