Access построитель выражений switch
Обновлено: 22.12.2024
Evaluates a list of expressions and returns a Variant value or an expression associated with the first expression in the list that is True.
Switch( expr-1, value-1 [, expr-2, value-2 ] … [, expr-n, value-n ] )
The Switch function syntax has these arguments:
Description
expr
Required. Variant expression you want to evaluate.
value
Required. Value or expression to be returned if the corresponding expression is True.
The Switch function argument list consists of pairs of expressions and values. The expressions are evaluated from left to right, and the value associated with the first expression to evaluate to True is returned. If the parts aren't properly paired, a run-time error occurs. For example, if expr-1 is True, Switch returns value-1. If expr-1 is False, but expr-2 is True, Switch returns value-2, and so on.
Switch returns a Null value if:
None of the expressions is True.
The first True expression has a corresponding value that is Null.
Switch evaluates all of the expressions, even though it returns only one of them. For this reason, you should watch for undesirable side effects. For example, if the evaluation of any expression results in a division by zero error, an error occurs.
Query example
SELECT ProductSales.ProductID, Switch([ProductID]="PRO_XYZ1","First",[ProductID]="PRO_XYZ2","Two",[ProductID]="PRO_XYZ1","Ten") AS testSwitch FROM ProductSales;
Returns the "ProductID", evaluates the expressions in "Switch" formula and switches the existing values with defined values for all the "True" expressions. For example: "PRO_XYZ1" is replaces by "First", "PRO_XYZ2" is replaces by "Two" and so on.
VBA example
Note: Examples that follow demonstrate the use of this function in a Visual Basic for Applications (VBA) module. For more information about working with VBA, select Developer Reference in the drop-down list next to Search and enter one or more terms in the search box.
This example uses the Switch function to return the name of a language that matches the name of a city.
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