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DMax Method

You can use the DMax functions to determine the maximum values in a specified set of records (a domain). Use the DMax functions in Visual Basic, a macro, a query expression, or a calculated control. Variant.

expression   Required. An expression that returns one of the objects in the Applies To list.

Expr  Required String. An expression that identifies the field for which you want to find the minimum or maximum value. It can be a string expression identifying a field in a table or query, or it can be an expression that performs a calculation on data in that field. In expr, you can include the name of a field in a table, a control on a form, a constant, or a function. If expr includes a function, it can be either built-in or user-defined, but not another domain aggregate or SQL aggregate function.

Domain  Required String. A string expression identifying the set of records that constitutes the domain. It can be a table name or a query name.

Criteria  Optional Variant. An optional string expression used to restrict the range of data on which the DMax function is performed. For example, criteria is often equivalent to the WHERE clause in an SQL expression, without the word WHERE. If criteria is omitted, the DMax function evaluates expr against the entire domain. Any field that is included in criteria must also be a field in domain, otherwise the DMax function returns a Null.

Remarks

The DMax function returns the maximum value that satisfies criteria. If expr identifies numeric data, the DMax function returns numeric values. If expr identifies string data, they return the string that is first or last alphabetically.

The DMax function ignores Null values in the field referenced by expr. However, if no record satisfies criteria or if domain contains no records, the DMax function returns a Null.

When you use the DMax function in a macro, module, query expression, or calculated control, you must construct the criteria argument carefully to ensure that it will be evaluated correctly.

You can use the DMax function to specify criteria in the Criteria row of a query, in a calculated field expression in a query, or in the Update To row of an update query.

Note   You can use the DMax function or theMax function in a calculated field expression in a totals query. If you use the DMax function, values are evaluated before the data is grouped. If you use the Max function, the data is grouped before values in the field expression are evaluated.

Use the DMax function in a calculated control when you need to specify criteria to restrict the range of data on which the function is performed. For example, to display the maximum freight charged for an order shipped to California, set the ControlSource property of a text box to the following expression:

=DMax("[Freight]", "Orders", "[ShipRegion] = 'CA'")

If you simply want to find the maximum value of all records in domain, use the Max function.

You can use the DMax function in a module or macro or in a calculated control on a form if the field that you need to display is not in the record source on which your form is based.

Tip   Although you can use the DMax function to find the maximum value from a field in a foreign table, it may be more efficient to create a query that contains the fields that you need from both tables, and base your form or report on that query.

Note   Unsaved changes to records in domain aren't included when you use these functions. If you want the DMax function to be based on the changed values, you must first save the changes by clicking Save Record on the File menu, moving the focus to another record, or by using the Update method.

Example

The following example returns the highest value from the Freight field for orders shipped to the United Kingdom. The domain is an Orders table. The criteria argument restricts the resulting set of records to those for which ShipCountry equals UK.

Dim curX As Currency, curY As Currency
curY = DMax("[Freight]", "Orders", "[ShipCountry] = 'UK'")

In the next example, the criteria argument includes the current value of a text box called OrderDate. The text box is bound to an OrderDate field in an Orders table. Note that the reference to the control isn't included in the double quotation marks (") that denote the strings. This ensures that each time the DMax function is called, Microsoft Access obtains the current value from the control.

Dim curX As Currency
curX = DMax("[Freight]", "Orders", "[OrderDate] = #" _
    & Forms!Orders!OrderDate & "#")