# Writing an expression in access 2010

Calculated fields perform calculations using data within one record, while totals rows perform a calculation on an entire field of data. Calculated fields When you create a calculated field, you are adding a new field in which every row contains a calculation involving other numerical fields in this row. To do this, you must enter a mathematical expression, which is made up of field names in your table and mathematical symbols. You don't need to know too much about math or expression-building to create a useful calculated field. The value of a control called "OrderID" in a report called "Invoice. For example, you can calculate a group total for the group footer in a report, or an order subtotal for line items on a form. You can also count the number of items in one or more fields or calculate an average value.

The expressions in the following table show some of the ways to use functions such as Avg, Count, and Sum. Top of Page SQL aggregate functions You use a type of function called an SQL or domain aggregate function when you need to sum or count values selectively. A "domain" consists of one or more fields in one or more tables, or one or more controls on one or more forms or reports.

For example, you can match the values in a table field with the values in a control on a form. Top of Page Date operations Tracking dates and times is a fundamental database activity.

For example, you can calculate how many days have elapsed since the invoice date to age your accounts receivable. You can format dates and times in numerous ways, as shown in the following table. Top of Page Conditions of only two values The example expressions in the following table use the IIf function to return one of two possible values.

You pass the IIf function three arguments: The first argument is an expression that must return a True or False value. The second argument is the value to return if the expression is true, and the third argument is the value to return if the expression is false.

Top of Page Queries and filters This section contains examples of expressions that you can use to create a calculated field in a query or to supply criteria to a query. A calculated field is a column in a query that results from an expression. For example, you can calculate a value, combine text values such as first and last names, or format a portion of a date.

You use criteria in a query to limit the records that you work with. For example, you can use the Between operator to supply a starting and ending date and limit the results of your query to orders that were shipped between those dates. The following provide examples of expressions for use in queries.

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Left [ProductName], 1 Creates a field called ProductInitial, and then uses the Left function to display, in the ProductInitial field, the first character of the value in the ProductName field.

Right [AssetCode], 2 Creates a field called TypeCode, and then uses the Right function to display the last two characters of the values in the AssetCode field.

Mid [Phone],2,3 Creates a field called AreaCode, and then uses the Mid function to display the three characters starting with the second character of the value in the Phone field.

Top of Page Arithmetic operations You can use expressions to add, subtract, multiply, and divide the values in two or more fields or controls. You can also perform arithmetic operations on dates. This expression uses the Sum function to total the values in the Freight field, and then divides those totals by the sum of the values in the Subtotal field.

To use this expression, you must convert your select query into a Totals query because you need to use the Total row in the design grid, and you must set the Total cell for this field to Expression.

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For more information about creating a Totals query, see the article Sum data by using a query.Mar 19,  · Before Access , Access supported a wide variety of expressions in different areas of the application.

Tables and fields, queries, form and report properties, controls, and macros can all use expressions to evaluate data or logic to drive the behavior of an application. In the past, each of these contexts in which an expression is used have shared a single, common expression evaluation engine.

Tip If you see the word expression in a menu, you can click it to start the Expression Builder. See it in action. The following video shows how to use the Expression Builder to create a common expression for a calculated field.

• Expressions, IIF Statements, and Conditional Formatting - Microsoft Community
• First things first, how do I find it?

An Access totals row adds up an entire column of data. Learn how to use them here. An Access calculated field lets you calculate data. Access - Tables: How to Create In fact, you can write robust expressions using only grade-school math.

For instance, you could: Use + to find the sum of the contents of two fields or to add a. Handout: Access Creating Reports Topics came directly from MS Access Help. ICT Training, Maxwell School of Syracuse University Page 4 Unbound control: A control that doesn't have a source of data (a field or expression) is an unbound.

Expression Builder i. Expression Builder in Access provides you just that with full support of applying functions and formulas. It can be used anywhere in Access with any database element like; Forms, Reports, Queries and Tables.

Once done writing condition, click OK to continue. Creating forms in Access can make entering data more convenient. Learn how to create and modify Access forms here. 